merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

10 files changed, 2903 insertions, 0 deletions

diff --git a/third_party/git/contrib/subtree/.gitignore b/third_party/git/contrib/subtree/.gitignore
new file mode 100644
index 000000000000..0b9381abcad3
--- /dev/null
+++ b/third_party/git/contrib/subtree/.gitignore
@@ -0,0 +1,7 @@
+*~
+git-subtree
+git-subtree.1
+git-subtree.html
+git-subtree.xml
+mainline
+subproj
diff --git a/third_party/git/contrib/subtree/COPYING b/third_party/git/contrib/subtree/COPYING
new file mode 100644
index 000000000000..d511905c1647
--- /dev/null
+++ b/third_party/git/contrib/subtree/COPYING
@@ -0,0 +1,339 @@
+		    GNU GENERAL PUBLIC LICENSE
+		       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+			    Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+		    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
+    machine-readable copy of the corresponding source code, to be
+    distributed under the terms of Sections 1 and 2 above on a medium
+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
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+operating system on which the executable runs, unless that component
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+
+If distribution of executable or object code is made by offering
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+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices.  Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+			    NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+		     END OF TERMS AND CONDITIONS
+
+	    How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/third_party/git/contrib/subtree/INSTALL b/third_party/git/contrib/subtree/INSTALL
new file mode 100644
index 000000000000..7ab0cf450967
--- /dev/null
+++ b/third_party/git/contrib/subtree/INSTALL
@@ -0,0 +1,28 @@
+HOW TO INSTALL git-subtree
+==========================
+
+First, build from the top source directory.
+
+Then, in contrib/subtree, run:
+
+  make
+  make install
+  make install-doc
+
+If you used configure to do the main build the git-subtree build will
+pick up those settings.  If not, you will likely have to provide a
+value for prefix:
+
+  make prefix=<some dir>
+  make prefix=<some dir> install
+  make prefix=<some dir> install-doc
+
+To run tests first copy git-subtree to the main build area so the
+newly-built git can find it:
+
+  cp git-subtree ../..
+
+Then:
+
+  make test
+
diff --git a/third_party/git/contrib/subtree/Makefile b/third_party/git/contrib/subtree/Makefile
new file mode 100644
index 000000000000..6906aae44147
--- /dev/null
+++ b/third_party/git/contrib/subtree/Makefile
@@ -0,0 +1,101 @@
+# The default target of this Makefile is...
+all::
+
+-include ../../config.mak.autogen
+-include ../../config.mak
+
+prefix ?= /usr/local
+gitexecdir ?= $(prefix)/libexec/git-core
+mandir ?= $(prefix)/share/man
+man1dir ?= $(mandir)/man1
+htmldir ?= $(prefix)/share/doc/git-doc
+
+../../GIT-VERSION-FILE: FORCE
+	$(MAKE) -C ../../ GIT-VERSION-FILE
+
+-include ../../GIT-VERSION-FILE
+
+# this should be set to a 'standard' bsd-type install program
+INSTALL  ?= install
+RM       ?= rm -f
+
+ASCIIDOC         = asciidoc
+ASCIIDOC_CONF    = -f ../../Documentation/asciidoc.conf
+ASCIIDOC_HTML    = xhtml11
+ASCIIDOC_DOCBOOK = docbook
+ASCIIDOC_EXTRA   =
+XMLTO            = xmlto
+
+ifdef USE_ASCIIDOCTOR
+ASCIIDOC         = asciidoctor
+ASCIIDOC_CONF    =
+ASCIIDOC_HTML    = xhtml5
+ASCIIDOC_DOCBOOK = docbook45
+ASCIIDOC_EXTRA  += -I../../Documentation -rasciidoctor-extensions
+ASCIIDOC_EXTRA  += -alitdd='&\#x2d;&\#x2d;'
+endif
+
+ifndef SHELL_PATH
+	SHELL_PATH = /bin/sh
+endif
+SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))
+
+MANPAGE_XSL   = ../../Documentation/manpage-normal.xsl
+
+GIT_SUBTREE_SH := git-subtree.sh
+GIT_SUBTREE    := git-subtree
+
+GIT_SUBTREE_DOC := git-subtree.1
+GIT_SUBTREE_XML := git-subtree.xml
+GIT_SUBTREE_TXT := git-subtree.txt
+GIT_SUBTREE_HTML := git-subtree.html
+GIT_SUBTREE_TEST := ../../git-subtree
+
+all:: $(GIT_SUBTREE)
+
+$(GIT_SUBTREE): $(GIT_SUBTREE_SH)
+	sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' $< >$@
+	chmod +x $@
+
+doc: $(GIT_SUBTREE_DOC) $(GIT_SUBTREE_HTML)
+
+man: $(GIT_SUBTREE_DOC)
+
+html: $(GIT_SUBTREE_HTML)
+
+install: $(GIT_SUBTREE)
+	$(INSTALL) -d -m 755 $(DESTDIR)$(gitexecdir)
+	$(INSTALL) -m 755 $(GIT_SUBTREE) $(DESTDIR)$(gitexecdir)
+
+install-doc: install-man install-html
+
+install-man: $(GIT_SUBTREE_DOC)
+	$(INSTALL) -d -m 755 $(DESTDIR)$(man1dir)
+	$(INSTALL) -m 644 $^ $(DESTDIR)$(man1dir)
+
+install-html: $(GIT_SUBTREE_HTML)
+	$(INSTALL) -d -m 755 $(DESTDIR)$(htmldir)
+	$(INSTALL) -m 644 $^ $(DESTDIR)$(htmldir)
+
+$(GIT_SUBTREE_DOC): $(GIT_SUBTREE_XML)
+	$(XMLTO) -m $(MANPAGE_XSL) man $^
+
+$(GIT_SUBTREE_XML): $(GIT_SUBTREE_TXT)
+	$(ASCIIDOC) -b $(ASCIIDOC_DOCBOOK) -d manpage $(ASCIIDOC_CONF) \
+		-agit_version=$(GIT_VERSION) $(ASCIIDOC_EXTRA) $^
+
+$(GIT_SUBTREE_HTML): $(GIT_SUBTREE_TXT)
+	$(ASCIIDOC) -b $(ASCIIDOC_HTML) -d manpage $(ASCIIDOC_CONF) \
+		-agit_version=$(GIT_VERSION) $(ASCIIDOC_EXTRA) $^
+
+$(GIT_SUBTREE_TEST): $(GIT_SUBTREE)
+	cp $< $@
+
+test: $(GIT_SUBTREE_TEST)
+	$(MAKE) -C t/ test
+
+clean:
+	$(RM) $(GIT_SUBTREE)
+	$(RM) *.xml *.html *.1
+
+.PHONY: FORCE
diff --git a/third_party/git/contrib/subtree/README b/third_party/git/contrib/subtree/README
new file mode 100644
index 000000000000..c686b4a69b12
--- /dev/null
+++ b/third_party/git/contrib/subtree/README
@@ -0,0 +1,8 @@
+
+Please read git-subtree.txt for documentation.
+
+Please don't contact me using github mail; it's slow, ugly, and worst of
+all, redundant. Email me instead at apenwarr@gmail.com and I'll be happy to
+help.
+
+Avery
diff --git a/third_party/git/contrib/subtree/git-subtree.sh b/third_party/git/contrib/subtree/git-subtree.sh
new file mode 100755
index 000000000000..868e18b9a1ab
--- /dev/null
+++ b/third_party/git/contrib/subtree/git-subtree.sh
@@ -0,0 +1,901 @@
+#!/bin/sh
+#
+# git-subtree.sh: split/join git repositories in subdirectories of this one
+#
+# Copyright (C) 2009 Avery Pennarun <apenwarr@gmail.com>
+#
+if test $# -eq 0
+then
+	set -- -h
+fi
+OPTS_SPEC="\
+git subtree add   --prefix=<prefix> <commit>
+git subtree add   --prefix=<prefix> <repository> <ref>
+git subtree merge --prefix=<prefix> <commit>
+git subtree pull  --prefix=<prefix> <repository> <ref>
+git subtree push  --prefix=<prefix> <repository> <ref>
+git subtree split --prefix=<prefix> <commit>
+--
+h,help        show the help
+q             quiet
+d             show debug messages
+P,prefix=     the name of the subdir to split out
+m,message=    use the given message as the commit message for the merge commit
+ options for 'split'
+annotate=     add a prefix to commit message of new commits
+b,branch=     create a new branch from the split subtree
+ignore-joins  ignore prior --rejoin commits
+onto=         try connecting new tree to an existing one
+rejoin        merge the new branch back into HEAD
+ options for 'add', 'merge', and 'pull'
+squash        merge subtree changes as a single commit
+"
+eval "$(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)"
+
+PATH=$PATH:$(git --exec-path)
+. git-sh-setup
+
+require_work_tree
+
+quiet=
+branch=
+debug=
+command=
+onto=
+rejoin=
+ignore_joins=
+annotate=
+squash=
+message=
+prefix=
+
+debug () {
+	if test -n "$debug"
+	then
+		printf "%s\n" "$*" >&2
+	fi
+}
+
+say () {
+	if test -z "$quiet"
+	then
+		printf "%s\n" "$*" >&2
+	fi
+}
+
+progress () {
+	if test -z "$quiet"
+	then
+		printf "%s\r" "$*" >&2
+	fi
+}
+
+assert () {
+	if ! "$@"
+	then
+		die "assertion failed: " "$@"
+	fi
+}
+
+ensure_single_rev () {
+	if test $# -ne 1
+	then
+		die "You must provide exactly one revision.  Got: '$@'"
+	fi
+}
+
+while test $# -gt 0
+do
+	opt="$1"
+	shift
+
+	case "$opt" in
+	-q)
+		quiet=1
+		;;
+	-d)
+		debug=1
+		;;
+	--annotate)
+		annotate="$1"
+		shift
+		;;
+	--no-annotate)
+		annotate=
+		;;
+	-b)
+		branch="$1"
+		shift
+		;;
+	-P)
+		prefix="${1%/}"
+		shift
+		;;
+	-m)
+		message="$1"
+		shift
+		;;
+	--no-prefix)
+		prefix=
+		;;
+	--onto)
+		onto="$1"
+		shift
+		;;
+	--no-onto)
+		onto=
+		;;
+	--rejoin)
+		rejoin=1
+		;;
+	--no-rejoin)
+		rejoin=
+		;;
+	--ignore-joins)
+		ignore_joins=1
+		;;
+	--no-ignore-joins)
+		ignore_joins=
+		;;
+	--squash)
+		squash=1
+		;;
+	--no-squash)
+		squash=
+		;;
+	--)
+		break
+		;;
+	*)
+		die "Unexpected option: $opt"
+		;;
+	esac
+done
+
+command="$1"
+shift
+
+case "$command" in
+add|merge|pull)
+	default=
+	;;
+split|push)
+	default="--default HEAD"
+	;;
+*)
+	die "Unknown command '$command'"
+	;;
+esac
+
+if test -z "$prefix"
+then
+	die "You must provide the --prefix option."
+fi
+
+case "$command" in
+add)
+	test -e "$prefix" &&
+		die "prefix '$prefix' already exists."
+	;;
+*)
+	test -e "$prefix" ||
+		die "'$prefix' does not exist; use 'git subtree add'"
+	;;
+esac
+
+dir="$(dirname "$prefix/.")"
+
+if test "$command" != "pull" &&
+		test "$command" != "add" &&
+		test "$command" != "push"
+then
+	revs=$(git rev-parse $default --revs-only "$@") || exit $?
+	dirs=$(git rev-parse --no-revs --no-flags "$@") || exit $?
+	ensure_single_rev $revs
+	if test -n "$dirs"
+	then
+		die "Error: Use --prefix instead of bare filenames."
+	fi
+fi
+
+debug "command: {$command}"
+debug "quiet: {$quiet}"
+debug "revs: {$revs}"
+debug "dir: {$dir}"
+debug "opts: {$*}"
+debug
+
+cache_setup () {
+	cachedir="$GIT_DIR/subtree-cache/$$"
+	rm -rf "$cachedir" ||
+		die "Can't delete old cachedir: $cachedir"
+	mkdir -p "$cachedir" ||
+		die "Can't create new cachedir: $cachedir"
+	mkdir -p "$cachedir/notree" ||
+		die "Can't create new cachedir: $cachedir/notree"
+	debug "Using cachedir: $cachedir" >&2
+}
+
+cache_get () {
+	for oldrev in "$@"
+	do
+		if test -r "$cachedir/$oldrev"
+		then
+			read newrev <"$cachedir/$oldrev"
+			echo $newrev
+		fi
+	done
+}
+
+cache_miss () {
+	for oldrev in "$@"
+	do
+		if ! test -r "$cachedir/$oldrev"
+		then
+			echo $oldrev
+		fi
+	done
+}
+
+check_parents () {
+	missed=$(cache_miss "$1")
+	local indent=$(($2 + 1))
+	for miss in $missed
+	do
+		if ! test -r "$cachedir/notree/$miss"
+		then
+			debug "  incorrect order: $miss"
+			process_split_commit "$miss" "" "$indent"
+		fi
+	done
+}
+
+set_notree () {
+	echo "1" > "$cachedir/notree/$1"
+}
+
+cache_set () {
+	oldrev="$1"
+	newrev="$2"
+	if test "$oldrev" != "latest_old" &&
+		test "$oldrev" != "latest_new" &&
+		test -e "$cachedir/$oldrev"
+	then
+		die "cache for $oldrev already exists!"
+	fi
+	echo "$newrev" >"$cachedir/$oldrev"
+}
+
+rev_exists () {
+	if git rev-parse "$1" >/dev/null 2>&1
+	then
+		return 0
+	else
+		return 1
+	fi
+}
+
+rev_is_descendant_of_branch () {
+	newrev="$1"
+	branch="$2"
+	branch_hash=$(git rev-parse "$branch")
+	match=$(git rev-list -1 "$branch_hash" "^$newrev")
+
+	if test -z "$match"
+	then
+		return 0
+	else
+		return 1
+	fi
+}
+
+# if a commit doesn't have a parent, this might not work.  But we only want
+# to remove the parent from the rev-list, and since it doesn't exist, it won't
+# be there anyway, so do nothing in that case.
+try_remove_previous () {
+	if rev_exists "$1^"
+	then
+		echo "^$1^"
+	fi
+}
+
+find_latest_squash () {
+	debug "Looking for latest squash ($dir)..."
+	dir="$1"
+	sq=
+	main=
+	sub=
+	git log --grep="^git-subtree-dir: $dir/*\$" \
+		--no-show-signature --pretty=format:'START %H%n%s%n%n%b%nEND%n' HEAD |
+	while read a b junk
+	do
+		debug "$a $b $junk"
+		debug "{{$sq/$main/$sub}}"
+		case "$a" in
+		START)
+			sq="$b"
+			;;
+		git-subtree-mainline:)
+			main="$b"
+			;;
+		git-subtree-split:)
+			sub="$(git rev-parse "$b^0")" ||
+			die "could not rev-parse split hash $b from commit $sq"
+			;;
+		END)
+			if test -n "$sub"
+			then
+				if test -n "$main"
+				then
+					# a rejoin commit?
+					# Pretend its sub was a squash.
+					sq="$sub"
+				fi
+				debug "Squash found: $sq $sub"
+				echo "$sq" "$sub"
+				break
+			fi
+			sq=
+			main=
+			sub=
+			;;
+		esac
+	done
+}
+
+find_existing_splits () {
+	debug "Looking for prior splits..."
+	dir="$1"
+	revs="$2"
+	main=
+	sub=
+	local grep_format="^git-subtree-dir: $dir/*\$"
+	if test -n "$ignore_joins"
+	then
+		grep_format="^Add '$dir/' from commit '"
+	fi
+	git log --grep="$grep_format" \
+		--no-show-signature --pretty=format:'START %H%n%s%n%n%b%nEND%n' $revs |
+	while read a b junk
+	do
+		case "$a" in
+		START)
+			sq="$b"
+			;;
+		git-subtree-mainline:)
+			main="$b"
+			;;
+		git-subtree-split:)
+			sub="$(git rev-parse "$b^0")" ||
+			die "could not rev-parse split hash $b from commit $sq"
+			;;
+		END)
+			debug "  Main is: '$main'"
+			if test -z "$main" -a -n "$sub"
+			then
+				# squash commits refer to a subtree
+				debug "  Squash: $sq from $sub"
+				cache_set "$sq" "$sub"
+			fi
+			if test -n "$main" -a -n "$sub"
+			then
+				debug "  Prior: $main -> $sub"
+				cache_set $main $sub
+				cache_set $sub $sub
+				try_remove_previous "$main"
+				try_remove_previous "$sub"
+			fi
+			main=
+			sub=
+			;;
+		esac
+	done
+}
+
+copy_commit () {
+	# We're going to set some environment vars here, so
+	# do it in a subshell to get rid of them safely later
+	debug copy_commit "{$1}" "{$2}" "{$3}"
+	git log -1 --no-show-signature --pretty=format:'%an%n%ae%n%aD%n%cn%n%ce%n%cD%n%B' "$1" |
+	(
+		read GIT_AUTHOR_NAME
+		read GIT_AUTHOR_EMAIL
+		read GIT_AUTHOR_DATE
+		read GIT_COMMITTER_NAME
+		read GIT_COMMITTER_EMAIL
+		read GIT_COMMITTER_DATE
+		export  GIT_AUTHOR_NAME \
+			GIT_AUTHOR_EMAIL \
+			GIT_AUTHOR_DATE \
+			GIT_COMMITTER_NAME \
+			GIT_COMMITTER_EMAIL \
+			GIT_COMMITTER_DATE
+		(
+			printf "%s" "$annotate"
+			cat
+		) |
+		git commit-tree "$2" $3  # reads the rest of stdin
+	) || die "Can't copy commit $1"
+}
+
+add_msg () {
+	dir="$1"
+	latest_old="$2"
+	latest_new="$3"
+	if test -n "$message"
+	then
+		commit_message="$message"
+	else
+		commit_message="Add '$dir/' from commit '$latest_new'"
+	fi
+	cat <<-EOF
+		$commit_message
+
+		git-subtree-dir: $dir
+		git-subtree-mainline: $latest_old
+		git-subtree-split: $latest_new
+	EOF
+}
+
+add_squashed_msg () {
+	if test -n "$message"
+	then
+		echo "$message"
+	else
+		echo "Merge commit '$1' as '$2'"
+	fi
+}
+
+rejoin_msg () {
+	dir="$1"
+	latest_old="$2"
+	latest_new="$3"
+	if test -n "$message"
+	then
+		commit_message="$message"
+	else
+		commit_message="Split '$dir/' into commit '$latest_new'"
+	fi
+	cat <<-EOF
+		$commit_message
+
+		git-subtree-dir: $dir
+		git-subtree-mainline: $latest_old
+		git-subtree-split: $latest_new
+	EOF
+}
+
+squash_msg () {
+	dir="$1"
+	oldsub="$2"
+	newsub="$3"
+	newsub_short=$(git rev-parse --short "$newsub")
+
+	if test -n "$oldsub"
+	then
+		oldsub_short=$(git rev-parse --short "$oldsub")
+		echo "Squashed '$dir/' changes from $oldsub_short..$newsub_short"
+		echo
+		git log --no-show-signature --pretty=tformat:'%h %s' "$oldsub..$newsub"
+		git log --no-show-signature --pretty=tformat:'REVERT: %h %s' "$newsub..$oldsub"
+	else
+		echo "Squashed '$dir/' content from commit $newsub_short"
+	fi
+
+	echo
+	echo "git-subtree-dir: $dir"
+	echo "git-subtree-split: $newsub"
+}
+
+toptree_for_commit () {
+	commit="$1"
+	git rev-parse --verify "$commit^{tree}" || exit $?
+}
+
+subtree_for_commit () {
+	commit="$1"
+	dir="$2"
+	git ls-tree "$commit" -- "$dir" |
+	while read mode type tree name
+	do
+		assert test "$name" = "$dir"
+		assert test "$type" = "tree" -o "$type" = "commit"
+		test "$type" = "commit" && continue  # ignore submodules
+		echo $tree
+		break
+	done
+}
+
+tree_changed () {
+	tree=$1
+	shift
+	if test $# -ne 1
+	then
+		return 0   # weird parents, consider it changed
+	else
+		ptree=$(toptree_for_commit $1)
+		if test "$ptree" != "$tree"
+		then
+			return 0   # changed
+		else
+			return 1   # not changed
+		fi
+	fi
+}
+
+new_squash_commit () {
+	old="$1"
+	oldsub="$2"
+	newsub="$3"
+	tree=$(toptree_for_commit $newsub) || exit $?
+	if test -n "$old"
+	then
+		squash_msg "$dir" "$oldsub" "$newsub" |
+		git commit-tree "$tree" -p "$old" || exit $?
+	else
+		squash_msg "$dir" "" "$newsub" |
+		git commit-tree "$tree" || exit $?
+	fi
+}
+
+copy_or_skip () {
+	rev="$1"
+	tree="$2"
+	newparents="$3"
+	assert test -n "$tree"
+
+	identical=
+	nonidentical=
+	p=
+	gotparents=
+	copycommit=
+	for parent in $newparents
+	do
+		ptree=$(toptree_for_commit $parent) || exit $?
+		test -z "$ptree" && continue
+		if test "$ptree" = "$tree"
+		then
+			# an identical parent could be used in place of this rev.
+			if test -n "$identical"
+			then
+				# if a previous identical parent was found, check whether
+				# one is already an ancestor of the other
+				mergebase=$(git merge-base $identical $parent)
+				if test "$identical" = "$mergebase"
+				then
+					# current identical commit is an ancestor of parent
+					identical="$parent"
+				elif test "$parent" != "$mergebase"
+				then
+					# no common history; commit must be copied
+					copycommit=1
+				fi
+			else
+				# first identical parent detected
+				identical="$parent"
+			fi
+		else
+			nonidentical="$parent"
+		fi
+
+		# sometimes both old parents map to the same newparent;
+		# eliminate duplicates
+		is_new=1
+		for gp in $gotparents
+		do
+			if test "$gp" = "$parent"
+			then
+				is_new=
+				break
+			fi
+		done
+		if test -n "$is_new"
+		then
+			gotparents="$gotparents $parent"
+			p="$p -p $parent"
+		fi
+	done
+
+	if test -n "$identical" && test -n "$nonidentical"
+	then
+		extras=$(git rev-list --count $identical..$nonidentical)
+		if test "$extras" -ne 0
+		then
+			# we need to preserve history along the other branch
+			copycommit=1
+		fi
+	fi
+	if test -n "$identical" && test -z "$copycommit"
+	then
+		echo $identical
+	else
+		copy_commit "$rev" "$tree" "$p" || exit $?
+	fi
+}
+
+ensure_clean () {
+	if ! git diff-index HEAD --exit-code --quiet 2>&1
+	then
+		die "Working tree has modifications.  Cannot add."
+	fi
+	if ! git diff-index --cached HEAD --exit-code --quiet 2>&1
+	then
+		die "Index has modifications.  Cannot add."
+	fi
+}
+
+ensure_valid_ref_format () {
+	git check-ref-format "refs/heads/$1" ||
+		die "'$1' does not look like a ref"
+}
+
+process_split_commit () {
+	local rev="$1"
+	local parents="$2"
+	local indent=$3
+
+	if test $indent -eq 0
+	then
+		revcount=$(($revcount + 1))
+	else
+		# processing commit without normal parent information;
+		# fetch from repo
+		parents=$(git rev-parse "$rev^@")
+		extracount=$(($extracount + 1))
+	fi
+
+	progress "$revcount/$revmax ($createcount) [$extracount]"
+
+	debug "Processing commit: $rev"
+	exists=$(cache_get "$rev")
+	if test -n "$exists"
+	then
+		debug "  prior: $exists"
+		return
+	fi
+	createcount=$(($createcount + 1))
+	debug "  parents: $parents"
+	check_parents "$parents" "$indent"
+	newparents=$(cache_get $parents)
+	debug "  newparents: $newparents"
+
+	tree=$(subtree_for_commit "$rev" "$dir")
+	debug "  tree is: $tree"
+
+	# ugly.  is there no better way to tell if this is a subtree
+	# vs. a mainline commit?  Does it matter?
+	if test -z "$tree"
+	then
+		set_notree "$rev"
+		if test -n "$newparents"
+		then
+			cache_set "$rev" "$rev"
+		fi
+		return
+	fi
+
+	newrev=$(copy_or_skip "$rev" "$tree" "$newparents") || exit $?
+	debug "  newrev is: $newrev"
+	cache_set "$rev" "$newrev"
+	cache_set latest_new "$newrev"
+	cache_set latest_old "$rev"
+}
+
+cmd_add () {
+	if test -e "$dir"
+	then
+		die "'$dir' already exists.  Cannot add."
+	fi
+
+	ensure_clean
+
+	if test $# -eq 1
+	then
+		git rev-parse -q --verify "$1^{commit}" >/dev/null ||
+			die "'$1' does not refer to a commit"
+
+		cmd_add_commit "$@"
+
+	elif test $# -eq 2
+	then
+		# Technically we could accept a refspec here but we're
+		# just going to turn around and add FETCH_HEAD under the
+		# specified directory.  Allowing a refspec might be
+		# misleading because we won't do anything with any other
+		# branches fetched via the refspec.
+		ensure_valid_ref_format "$2"
+
+		cmd_add_repository "$@"
+	else
+		say "error: parameters were '$@'"
+		die "Provide either a commit or a repository and commit."
+	fi
+}
+
+cmd_add_repository () {
+	echo "git fetch" "$@"
+	repository=$1
+	refspec=$2
+	git fetch "$@" || exit $?
+	revs=FETCH_HEAD
+	set -- $revs
+	cmd_add_commit "$@"
+}
+
+cmd_add_commit () {
+	rev=$(git rev-parse $default --revs-only "$@") || exit $?
+	ensure_single_rev $rev
+
+	debug "Adding $dir as '$rev'..."
+	git read-tree --prefix="$dir" $rev || exit $?
+	git checkout -- "$dir" || exit $?
+	tree=$(git write-tree) || exit $?
+
+	headrev=$(git rev-parse HEAD) || exit $?
+	if test -n "$headrev" && test "$headrev" != "$rev"
+	then
+		headp="-p $headrev"
+	else
+		headp=
+	fi
+
+	if test -n "$squash"
+	then
+		rev=$(new_squash_commit "" "" "$rev") || exit $?
+		commit=$(add_squashed_msg "$rev" "$dir" |
+			git commit-tree "$tree" $headp -p "$rev") || exit $?
+	else
+		revp=$(peel_committish "$rev") &&
+		commit=$(add_msg "$dir" $headrev "$rev" |
+			git commit-tree "$tree" $headp -p "$revp") || exit $?
+	fi
+	git reset "$commit" || exit $?
+
+	say "Added dir '$dir'"
+}
+
+cmd_split () {
+	debug "Splitting $dir..."
+	cache_setup || exit $?
+
+	if test -n "$onto"
+	then
+		debug "Reading history for --onto=$onto..."
+		git rev-list $onto |
+		while read rev
+		do
+			# the 'onto' history is already just the subdir, so
+			# any parent we find there can be used verbatim
+			debug "  cache: $rev"
+			cache_set "$rev" "$rev"
+		done
+	fi
+
+	unrevs="$(find_existing_splits "$dir" "$revs")"
+
+	# We can't restrict rev-list to only $dir here, because some of our
+	# parents have the $dir contents the root, and those won't match.
+	# (and rev-list --follow doesn't seem to solve this)
+	grl='git rev-list --topo-order --reverse --parents $revs $unrevs'
+	revmax=$(eval "$grl" | wc -l)
+	revcount=0
+	createcount=0
+	extracount=0
+	eval "$grl" |
+	while read rev parents
+	do
+		process_split_commit "$rev" "$parents" 0
+	done || exit $?
+
+	latest_new=$(cache_get latest_new)
+	if test -z "$latest_new"
+	then
+		die "No new revisions were found"
+	fi
+
+	if test -n "$rejoin"
+	then
+		debug "Merging split branch into HEAD..."
+		latest_old=$(cache_get latest_old)
+		git merge -s ours \
+			--allow-unrelated-histories \
+			-m "$(rejoin_msg "$dir" "$latest_old" "$latest_new")" \
+			"$latest_new" >&2 || exit $?
+	fi
+	if test -n "$branch"
+	then
+		if rev_exists "refs/heads/$branch"
+		then
+			if ! rev_is_descendant_of_branch "$latest_new" "$branch"
+			then
+				die "Branch '$branch' is not an ancestor of commit '$latest_new'."
+			fi
+			action='Updated'
+		else
+			action='Created'
+		fi
+		git update-ref -m 'subtree split' \
+			"refs/heads/$branch" "$latest_new" || exit $?
+		say "$action branch '$branch'"
+	fi
+	echo "$latest_new"
+	exit 0
+}
+
+cmd_merge () {
+	rev=$(git rev-parse $default --revs-only "$@") || exit $?
+	ensure_single_rev $rev
+	ensure_clean
+
+	if test -n "$squash"
+	then
+		first_split="$(find_latest_squash "$dir")"
+		if test -z "$first_split"
+		then
+			die "Can't squash-merge: '$dir' was never added."
+		fi
+		set $first_split
+		old=$1
+		sub=$2
+		if test "$sub" = "$rev"
+		then
+			say "Subtree is already at commit $rev."
+			exit 0
+		fi
+		new=$(new_squash_commit "$old" "$sub" "$rev") || exit $?
+		debug "New squash commit: $new"
+		rev="$new"
+	fi
+
+	version=$(git version)
+	if test "$version" \< "git version 1.7"
+	then
+		if test -n "$message"
+		then
+			git merge -s subtree --message="$message" "$rev"
+		else
+			git merge -s subtree "$rev"
+		fi
+	else
+		if test -n "$message"
+		then
+			git merge -Xsubtree="$prefix" \
+				--message="$message" "$rev"
+		else
+			git merge -Xsubtree="$prefix" $rev
+		fi
+	fi
+}
+
+cmd_pull () {
+	if test $# -ne 2
+	then
+		die "You must provide <repository> <ref>"
+	fi
+	ensure_clean
+	ensure_valid_ref_format "$2"
+	git fetch "$@" || exit $?
+	revs=FETCH_HEAD
+	set -- $revs
+	cmd_merge "$@"
+}
+
+cmd_push () {
+	if test $# -ne 2
+	then
+		die "You must provide <repository> <ref>"
+	fi
+	ensure_valid_ref_format "$2"
+	if test -e "$dir"
+	then
+		repository=$1
+		refspec=$2
+		echo "git push using: " "$repository" "$refspec"
+		localrev=$(git subtree split --prefix="$prefix") || die
+		git push "$repository" "$localrev":"refs/heads/$refspec"
+	else
+		die "'$dir' must already exist. Try 'git subtree add'."
+	fi
+}
+
+"cmd_$command" "$@"
diff --git a/third_party/git/contrib/subtree/git-subtree.txt b/third_party/git/contrib/subtree/git-subtree.txt
new file mode 100644
index 000000000000..352deda69dcf
--- /dev/null
+++ b/third_party/git/contrib/subtree/git-subtree.txt
@@ -0,0 +1,351 @@
+git-subtree(1)
+==============
+
+NAME
+----
+git-subtree - Merge subtrees together and split repository into subtrees
+
+
+SYNOPSIS
+--------
+[verse]
+'git subtree' add   -P <prefix> <commit>
+'git subtree' add   -P <prefix> <repository> <ref>
+'git subtree' pull  -P <prefix> <repository> <ref>
+'git subtree' push  -P <prefix> <repository> <ref>
+'git subtree' merge -P <prefix> <commit>
+'git subtree' split -P <prefix> [OPTIONS] [<commit>]
+
+
+DESCRIPTION
+-----------
+Subtrees allow subprojects to be included within a subdirectory
+of the main project, optionally including the subproject's
+entire history.
+
+For example, you could include the source code for a library
+as a subdirectory of your application.
+
+Subtrees are not to be confused with submodules, which are meant for
+the same task. Unlike submodules, subtrees do not need any special
+constructions (like .gitmodules files or gitlinks) be present in
+your repository, and do not force end-users of your
+repository to do anything special or to understand how subtrees
+work. A subtree is just a subdirectory that can be
+committed to, branched, and merged along with your project in
+any way you want.
+
+They are also not to be confused with using the subtree merge
+strategy. The main difference is that, besides merging
+the other project as a subdirectory, you can also extract the
+entire history of a subdirectory from your project and make it
+into a standalone project. Unlike the subtree merge strategy
+you can alternate back and forth between these
+two operations. If the standalone library gets updated, you can
+automatically merge the changes into your project; if you
+update the library inside your project, you can "split" the
+changes back out again and merge them back into the library
+project.
+
+For example, if a library you made for one application ends up being
+useful elsewhere, you can extract its entire history and publish
+that as its own git repository, without accidentally
+intermingling the history of your application project.
+
+[TIP]
+In order to keep your commit messages clean, we recommend that
+people split their commits between the subtrees and the main
+project as much as possible.  That is, if you make a change that
+affects both the library and the main application, commit it in
+two pieces.  That way, when you split the library commits out
+later, their descriptions will still make sense.  But if this
+isn't important to you, it's not *necessary*.  git subtree will
+simply leave out the non-library-related parts of the commit
+when it splits it out into the subproject later.
+
+
+COMMANDS
+--------
+add::
+	Create the <prefix> subtree by importing its contents
+	from the given <commit> or <repository> and remote <ref>.
+	A new commit is created	automatically, joining the imported
+	project's history with your own.  With '--squash', imports
+	only a single commit from the subproject, rather than its
+	entire history.
+
+merge::
+	Merge recent changes up to <commit> into the <prefix>
+	subtree.  As with normal 'git merge', this doesn't
+	remove your own local changes; it just merges those
+	changes into the latest <commit>.  With '--squash',
+	creates only one commit that contains all the changes,
+	rather than merging in the entire history.
++
+If you use '--squash', the merge direction doesn't always have to be
+forward; you can use this command to go back in time from v2.5 to v2.4,
+for example.  If your merge introduces a conflict, you can resolve it in
+the usual ways.
+	
+pull::
+	Exactly like 'merge', but parallels 'git pull' in that
+	it fetches the given ref from the specified remote
+	repository.
+	
+push::
+	Does a 'split' (see below) using the <prefix> supplied
+	and then does a 'git push' to push the result to the 
+	repository and ref. This can be used to push your
+	subtree to different branches of the remote repository.
+
+split::
+	Extract a new, synthetic project history from the
+	history of the <prefix> subtree.  The new history
+	includes only the commits (including merges) that
+	affected <prefix>, and each of those commits now has the
+	contents of <prefix> at the root of the project instead
+	of in a subdirectory.  Thus, the newly created history
+	is suitable for export as a separate git repository.
++
+After splitting successfully, a single commit id is printed to stdout.
+This corresponds to the HEAD of the newly created tree, which you can
+manipulate however you want.
++
+Repeated splits of exactly the same history are guaranteed to be
+identical (i.e. to produce the same commit ids).  Because of this, if
+you add new commits and then re-split, the new commits will be attached
+as commits on top of the history you generated last time, so 'git merge'
+and friends will work as expected.
++
+Note that if you use '--squash' when you merge, you should usually not
+just '--rejoin' when you split.
+
+
+OPTIONS
+-------
+-q::
+--quiet::
+	Suppress unnecessary output messages on stderr.
+
+-d::
+--debug::
+	Produce even more unnecessary output messages on stderr.
+
+-P <prefix>::
+--prefix=<prefix>::
+	Specify the path in the repository to the subtree you
+	want to manipulate.  This option is mandatory
+	for all commands.
+
+-m <message>::
+--message=<message>::
+	This option is only valid for add, merge and pull (unsure).
+	Specify <message> as the commit message for the merge commit.
+
+
+OPTIONS FOR add, merge, push, pull
+----------------------------------
+--squash::
+	This option is only valid for add, merge, and pull
+	commands.
++
+Instead of merging the entire history from the subtree project, produce
+only a single commit that contains all the differences you want to
+merge, and then merge that new commit into your project.
++
+Using this option helps to reduce log clutter. People rarely want to see
+every change that happened between v1.0 and v1.1 of the library they're
+using, since none of the interim versions were ever included in their
+application.
++
+Using '--squash' also helps avoid problems when the same subproject is
+included multiple times in the same project, or is removed and then
+re-added.  In such a case, it doesn't make sense to combine the
+histories anyway, since it's unclear which part of the history belongs
+to which subtree.
++
+Furthermore, with '--squash', you can switch back and forth between
+different versions of a subtree, rather than strictly forward.  'git
+subtree merge --squash' always adjusts the subtree to match the exactly
+specified commit, even if getting to that commit would require undoing
+some changes that were added earlier.
++
+Whether or not you use '--squash', changes made in your local repository
+remain intact and can be later split and send upstream to the
+subproject.
+
+
+OPTIONS FOR split
+-----------------
+--annotate=<annotation>::
+	This option is only valid for the split command.
++
+When generating synthetic history, add <annotation> as a prefix to each
+commit message.  Since we're creating new commits with the same commit
+message, but possibly different content, from the original commits, this
+can help to differentiate them and avoid confusion.
++
+Whenever you split, you need to use the same <annotation>, or else you
+don't have a guarantee that the new re-created history will be identical
+to the old one.  That will prevent merging from working correctly.  git
+subtree tries to make it work anyway, particularly if you use --rejoin,
+but it may not always be effective.
+
+-b <branch>::
+--branch=<branch>::
+	This option is only valid for the split command.
++
+After generating the synthetic history, create a new branch called
+<branch> that contains the new history.  This is suitable for immediate
+pushing upstream.  <branch> must not already exist.
+
+--ignore-joins::
+	This option is only valid for the split command.
++
+If you use '--rejoin', git subtree attempts to optimize its history
+reconstruction to generate only the new commits since the last
+'--rejoin'.  '--ignore-join' disables this behaviour, forcing it to
+regenerate the entire history.  In a large project, this can take a long
+time.
+
+--onto=<onto>::
+	This option is only valid for the split command.
++
+If your subtree was originally imported using something other than git
+subtree, its history may not match what git subtree is expecting.  In
+that case, you can specify the commit id <onto> that corresponds to the
+first revision of the subproject's history that was imported into your
+project, and git subtree will attempt to build its history from there.
++
+If you used 'git subtree add', you should never need this option.
+
+--rejoin::
+	This option is only valid for the split command.
++
+After splitting, merge the newly created synthetic history back into
+your main project.  That way, future splits can search only the part of
+history that has been added since the most recent --rejoin.
++
+If your split commits end up merged into the upstream subproject, and
+then you want to get the latest upstream version, this will allow git's
+merge algorithm to more intelligently avoid conflicts (since it knows
+these synthetic commits are already part of the upstream repository).
++
+Unfortunately, using this option results in 'git log' showing an extra
+copy of every new commit that was created (the original, and the
+synthetic one).
++
+If you do all your merges with '--squash', don't use '--rejoin' when you
+split, because you don't want the subproject's history to be part of
+your project anyway.
+
+
+EXAMPLE 1. Add command
+----------------------
+Let's assume that you have a local repository that you would like
+to add an external vendor library to. In this case we will add the
+git-subtree repository as a subdirectory of your already existing
+git-extensions repository in ~/git-extensions/:
+
+	$ git subtree add --prefix=git-subtree --squash \
+		git://github.com/apenwarr/git-subtree.git master
+
+'master' needs to be a valid remote ref and can be a different branch
+name
+
+You can omit the --squash flag, but doing so will increase the number
+of commits that are included in your local repository.
+
+We now have a ~/git-extensions/git-subtree directory containing code
+from the master branch of git://github.com/apenwarr/git-subtree.git
+in our git-extensions repository.
+
+EXAMPLE 2. Extract a subtree using commit, merge and pull
+---------------------------------------------------------
+Let's use the repository for the git source code as an example.
+First, get your own copy of the git.git repository:
+
+	$ git clone git://git.kernel.org/pub/scm/git/git.git test-git
+	$ cd test-git
+
+gitweb (commit 1130ef3) was merged into git as of commit
+0a8f4f0, after which it was no longer maintained separately. 
+But imagine it had been maintained separately, and we wanted to
+extract git's changes to gitweb since that time, to share with
+the upstream.  You could do this:
+
+	$ git subtree split --prefix=gitweb --annotate='(split) ' \
+        	0a8f4f0^.. --onto=1130ef3 --rejoin \
+        	--branch gitweb-latest
+        $ gitk gitweb-latest
+        $ git push git@github.com:whatever/gitweb.git gitweb-latest:master
+        
+(We use '0a8f4f0^..' because that means "all the changes from
+0a8f4f0 to the current version, including 0a8f4f0 itself.")
+
+If gitweb had originally been merged using 'git subtree add' (or
+a previous split had already been done with --rejoin specified)
+then you can do all your splits without having to remember any
+weird commit ids:
+
+	$ git subtree split --prefix=gitweb --annotate='(split) ' --rejoin \
+		--branch gitweb-latest2
+
+And you can merge changes back in from the upstream project just
+as easily:
+
+	$ git subtree pull --prefix=gitweb \
+		git@github.com:whatever/gitweb.git master
+
+Or, using '--squash', you can actually rewind to an earlier
+version of gitweb:
+
+	$ git subtree merge --prefix=gitweb --squash gitweb-latest~10
+
+Then make some changes:
+
+	$ date >gitweb/myfile
+	$ git add gitweb/myfile
+	$ git commit -m 'created myfile'
+
+And fast forward again:
+
+	$ git subtree merge --prefix=gitweb --squash gitweb-latest
+
+And notice that your change is still intact:
+	
+	$ ls -l gitweb/myfile
+
+And you can split it out and look at your changes versus
+the standard gitweb:
+
+	git log gitweb-latest..$(git subtree split --prefix=gitweb)
+
+EXAMPLE 3. Extract a subtree using branch
+-----------------------------------------
+Suppose you have a source directory with many files and
+subdirectories, and you want to extract the lib directory to its own
+git project. Here's a short way to do it:
+
+First, make the new repository wherever you want:
+
+	$ <go to the new location>
+	$ git init --bare
+
+Back in your original directory:
+
+	$ git subtree split --prefix=lib --annotate="(split)" -b split
+
+Then push the new branch onto the new empty repository:
+
+	$ git push <new-repo> split:master
+
+
+AUTHOR
+------
+Written by Avery Pennarun <apenwarr@gmail.com>
+
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/third_party/git/contrib/subtree/t/Makefile b/third_party/git/contrib/subtree/t/Makefile
new file mode 100644
index 000000000000..276898eb6bd7
--- /dev/null
+++ b/third_party/git/contrib/subtree/t/Makefile
@@ -0,0 +1,86 @@
+# Run tests
+#
+# Copyright (c) 2005 Junio C Hamano
+#
+
+-include ../../../config.mak.autogen
+-include ../../../config.mak
+
+#GIT_TEST_OPTS=--verbose --debug
+SHELL_PATH ?= $(SHELL)
+PERL_PATH ?= /usr/bin/perl
+TAR ?= $(TAR)
+RM ?= rm -f
+PROVE ?= prove
+DEFAULT_TEST_TARGET ?= test
+TEST_LINT ?= test-lint
+
+ifdef TEST_OUTPUT_DIRECTORY
+TEST_RESULTS_DIRECTORY = $(TEST_OUTPUT_DIRECTORY)/test-results
+else
+TEST_RESULTS_DIRECTORY = ../../../t/test-results
+endif
+
+# Shell quote;
+SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))
+PERL_PATH_SQ = $(subst ','\'',$(PERL_PATH))
+TEST_RESULTS_DIRECTORY_SQ = $(subst ','\'',$(TEST_RESULTS_DIRECTORY))
+
+T = $(sort $(wildcard t[0-9][0-9][0-9][0-9]-*.sh))
+TSVN = $(sort $(wildcard t91[0-9][0-9]-*.sh))
+TGITWEB = $(sort $(wildcard t95[0-9][0-9]-*.sh))
+THELPERS = $(sort $(filter-out $(T),$(wildcard *.sh)))
+
+all: $(DEFAULT_TEST_TARGET)
+
+test: pre-clean $(TEST_LINT)
+	$(MAKE) aggregate-results-and-cleanup
+
+prove: pre-clean $(TEST_LINT)
+	@echo "*** prove ***"; GIT_CONFIG=.git/config $(PROVE) --exec '$(SHELL_PATH_SQ)' $(GIT_PROVE_OPTS) $(T) :: $(GIT_TEST_OPTS)
+	$(MAKE) clean-except-prove-cache
+
+$(T):
+	@echo "*** $@ ***"; GIT_CONFIG=.git/config '$(SHELL_PATH_SQ)' $@ $(GIT_TEST_OPTS)
+
+pre-clean:
+	$(RM) -r '$(TEST_RESULTS_DIRECTORY_SQ)'
+
+clean-except-prove-cache:
+	$(RM) -r 'trash directory'.* '$(TEST_RESULTS_DIRECTORY_SQ)'
+	$(RM) -r valgrind/bin
+
+clean: clean-except-prove-cache
+	$(RM) .prove
+
+test-lint: test-lint-duplicates test-lint-executable test-lint-shell-syntax
+
+test-lint-duplicates:
+	@dups=`echo $(T) | tr ' ' '\n' | sed 's/-.*//' | sort | uniq -d` && \
+		test -z "$$dups" || { \
+		echo >&2 "duplicate test numbers:" $$dups; exit 1; }
+
+test-lint-executable:
+	@bad=`for i in $(T); do test -x "$$i" || echo $$i; done` && \
+		test -z "$$bad" || { \
+		echo >&2 "non-executable tests:" $$bad; exit 1; }
+
+test-lint-shell-syntax:
+	@'$(PERL_PATH_SQ)' ../../../t/check-non-portable-shell.pl $(T) $(THELPERS)
+
+aggregate-results-and-cleanup: $(T)
+	$(MAKE) aggregate-results
+	$(MAKE) clean
+
+aggregate-results:
+	for f in '$(TEST_RESULTS_DIRECTORY_SQ)'/t*-*.counts; do \
+		echo "$$f"; \
+	done | '$(SHELL_PATH_SQ)' ../../../t/aggregate-results.sh
+
+valgrind:
+	$(MAKE) GIT_TEST_OPTS="$(GIT_TEST_OPTS) --valgrind"
+
+test-results:
+	mkdir -p test-results
+
+.PHONY: pre-clean $(T) aggregate-results clean valgrind
diff --git a/third_party/git/contrib/subtree/t/t7900-subtree.sh b/third_party/git/contrib/subtree/t/t7900-subtree.sh
new file mode 100755
index 000000000000..57ff4b25c17e
--- /dev/null
+++ b/third_party/git/contrib/subtree/t/t7900-subtree.sh
@@ -0,0 +1,1034 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Avery Pennaraum
+# Copyright (c) 2015 Alexey Shumkin
+#
+test_description='Basic porcelain support for subtrees
+
+This test verifies the basic operation of the add, pull, merge
+and split subcommands of git subtree.
+'
+
+TEST_DIRECTORY=$(pwd)/../../../t
+export TEST_DIRECTORY
+
+. ../../../t/test-lib.sh
+
+subtree_test_create_repo()
+{
+	test_create_repo "$1" &&
+	(
+		cd "$1" &&
+		git config log.date relative
+	)
+}
+
+create()
+{
+	echo "$1" >"$1" &&
+	git add "$1"
+}
+
+check_equal()
+{
+	test_debug 'echo'
+	test_debug "echo \"check a:\" \"{$1}\""
+	test_debug "echo \"      b:\" \"{$2}\""
+	if [ "$1" = "$2" ]; then
+		return 0
+	else
+		return 1
+	fi
+}
+
+undo()
+{
+	git reset --hard HEAD~
+}
+
+# Make sure no patch changes more than one file.
+# The original set of commits changed only one file each.
+# A multi-file change would imply that we pruned commits
+# too aggressively.
+join_commits()
+{
+	commit=
+	all=
+	while read x y; do
+		if [ -z "$x" ]; then
+			continue
+		elif [ "$x" = "commit:" ]; then
+			if [ -n "$commit" ]; then
+				echo "$commit $all"
+				all=
+			fi
+			commit="$y"
+		else
+			all="$all $y"
+		fi
+	done
+	echo "$commit $all"
+}
+
+test_create_commit() (
+	repo=$1 &&
+	commit=$2 &&
+	cd "$repo" &&
+	mkdir -p "$(dirname "$commit")" \
+	|| error "Could not create directory for commit"
+	echo "$commit" >"$commit" &&
+	git add "$commit" || error "Could not add commit"
+	git commit -m "$commit" || error "Could not commit"
+)
+
+last_commit_message()
+{
+	git log --pretty=format:%s -1
+}
+
+subtree_test_count=0
+next_test() {
+	subtree_test_count=$(($subtree_test_count+1))
+}
+
+#
+# Tests for 'git subtree add'
+#
+
+next_test
+test_expect_success 'no merge from non-existent subtree' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		test_must_fail git subtree merge --prefix="sub dir" FETCH_HEAD
+	)
+'
+
+next_test
+test_expect_success 'no pull from non-existent subtree' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		test_must_fail git subtree pull --prefix="sub dir" ./"sub proj" master
+	)'
+
+next_test
+test_expect_success 'add subproj as subtree into sub dir/ with --prefix' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Add '\''sub dir/'\'' from commit '\''$(git rev-parse FETCH_HEAD)'\''"
+	)
+'
+
+next_test
+test_expect_success 'add subproj as subtree into sub dir/ with --prefix and --message' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" --message="Added subproject" FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Added subproject"
+	)
+'
+
+next_test
+test_expect_success 'add subproj as subtree into sub dir/ with --prefix as -P and --message as -m' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add -P "sub dir" -m "Added subproject" FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Added subproject"
+	)
+'
+
+next_test
+test_expect_success 'add subproj as subtree into sub dir/ with --squash and --prefix and --message' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" --message="Added subproject with squash" --squash FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Added subproject with squash"
+	)
+'
+
+#
+# Tests for 'git subtree merge'
+#
+
+next_test
+test_expect_success 'merge new subproj history into sub dir/ with --prefix' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Merge commit '\''$(git rev-parse FETCH_HEAD)'\''"
+	)
+'
+
+next_test
+test_expect_success 'merge new subproj history into sub dir/ with --prefix and --message' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" --message="Merged changes from subproject" FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Merged changes from subproject"
+	)
+'
+
+next_test
+test_expect_success 'merge new subproj history into sub dir/ with --squash and --prefix and --message' '
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	subtree_test_create_repo "$subtree_test_count" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" --message="Merged changes from subproject using squash" --squash FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Merged changes from subproject using squash"
+	)
+'
+
+next_test
+test_expect_success 'merge the added subproj again, should do nothing' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD &&
+		# this shouldn not actually do anything, since FETCH_HEAD
+		# is already a parent
+		result=$(git merge -s ours -m "merge -s -ours" FETCH_HEAD) &&
+		check_equal "${result}" "Already up to date."
+	)
+'
+
+next_test
+test_expect_success 'merge new subproj history into subdir/ with a slash appended to the argument of --prefix' '
+	test_create_repo "$test_count" &&
+	test_create_repo "$test_count/subproj" &&
+	test_create_commit "$test_count" main1 &&
+	test_create_commit "$test_count/subproj" sub1 &&
+	(
+		cd "$test_count" &&
+		git fetch ./subproj master &&
+		git subtree add --prefix=subdir/ FETCH_HEAD
+	) &&
+	test_create_commit "$test_count/subproj" sub2 &&
+	(
+		cd "$test_count" &&
+		git fetch ./subproj master &&
+		git subtree merge --prefix=subdir/ FETCH_HEAD &&
+		check_equal "$(last_commit_message)" "Merge commit '\''$(git rev-parse FETCH_HEAD)'\''"
+	)
+'
+
+#
+# Tests for 'git subtree split'
+#
+
+next_test
+test_expect_success 'split requires option --prefix' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD &&
+		echo "You must provide the --prefix option." > expected &&
+		test_must_fail git subtree split > actual 2>&1 &&
+		test_debug "printf '"expected: "'" &&
+		test_debug "cat expected" &&
+		test_debug "printf '"actual: "'" &&
+		test_debug "cat actual" &&
+		test_cmp expected actual
+	)
+'
+
+next_test
+test_expect_success 'split requires path given by option --prefix must exist' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD &&
+		echo "'\''non-existent-directory'\'' does not exist; use '\''git subtree add'\''" > expected &&
+		test_must_fail git subtree split --prefix=non-existent-directory > actual 2>&1 &&
+		test_debug "printf '"expected: "'" &&
+		test_debug "cat expected" &&
+		test_debug "printf '"actual: "'" &&
+		test_debug "cat actual" &&
+		test_cmp expected actual
+	)
+'
+
+next_test
+test_expect_success 'split sub dir/ with --rejoin' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		split_hash=$(git subtree split --prefix="sub dir" --annotate="*") &&
+		git subtree split --prefix="sub dir" --annotate="*" --rejoin &&
+		check_equal "$(last_commit_message)" "Split '\''sub dir/'\'' into commit '\''$split_hash'\''"
+	)
+ '
+
+next_test
+test_expect_success 'split sub dir/ with --rejoin from scratch' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	(
+		cd "$subtree_test_count" &&
+		mkdir "sub dir" &&
+		echo file >"sub dir"/file &&
+		git add "sub dir/file" &&
+		git commit -m"sub dir file" &&
+		split_hash=$(git subtree split --prefix="sub dir" --rejoin) &&
+		git subtree split --prefix="sub dir" --rejoin &&
+		check_equal "$(last_commit_message)" "Split '\''sub dir/'\'' into commit '\''$split_hash'\''"
+	)
+ '
+
+next_test
+test_expect_success 'split sub dir/ with --rejoin and --message' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --message="Split & rejoin" --annotate="*" --rejoin &&
+		check_equal "$(last_commit_message)" "Split & rejoin"
+	)
+'
+
+next_test
+test_expect_success 'split "sub dir"/ with --branch' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		split_hash=$(git subtree split --prefix="sub dir" --annotate="*") &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br &&
+		check_equal "$(git rev-parse subproj-br)" "$split_hash"
+	)
+'
+
+next_test
+test_expect_success 'check hash of split' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		split_hash=$(git subtree split --prefix="sub dir" --annotate="*") &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br &&
+		check_equal "$(git rev-parse subproj-br)" "$split_hash" &&
+		# Check hash of split
+		new_hash=$(git rev-parse subproj-br^2) &&
+		(
+			cd ./"sub proj" &&
+			subdir_hash=$(git rev-parse HEAD) &&
+			check_equal ''"$new_hash"'' "$subdir_hash"
+		)
+	)
+'
+
+next_test
+test_expect_success 'split "sub dir"/ with --branch for an existing branch' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git branch subproj-br FETCH_HEAD &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		split_hash=$(git subtree split --prefix="sub dir" --annotate="*") &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br &&
+		check_equal "$(git rev-parse subproj-br)" "$split_hash"
+	)
+'
+
+next_test
+test_expect_success 'split "sub dir"/ with --branch for an incompatible branch' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git branch init HEAD &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		test_must_fail git subtree split --prefix="sub dir" --branch init
+	)
+'
+
+#
+# Validity checking
+#
+
+next_test
+test_expect_success 'make sure exactly the right set of files ends up in the subproj' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub3 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD &&
+
+		test_write_lines main-sub1 main-sub2 main-sub3 main-sub4 \
+			sub1 sub2 sub3 sub4 >expect &&
+		git ls-files >actual &&
+		test_cmp expect actual
+	)
+'
+
+next_test
+test_expect_success 'make sure the subproj *only* contains commits that affect the "sub dir"' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub3 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD &&
+
+		test_write_lines main-sub1 main-sub2 main-sub3 main-sub4 \
+			sub1 sub2 sub3 sub4 >expect &&
+		git log --name-only --pretty=format:"" >log &&
+		sort <log | sed "/^\$/ d" >actual &&
+		test_cmp expect actual
+	)
+'
+
+next_test
+test_expect_success 'make sure exactly the right set of files ends up in the mainline' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub3 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree pull --prefix="sub dir" ./"sub proj" master &&
+
+		test_write_lines main1 main2 >chkm &&
+		test_write_lines main-sub1 main-sub2 main-sub3 main-sub4 >chkms &&
+		sed "s,^,sub dir/," chkms >chkms_sub &&
+		test_write_lines sub1 sub2 sub3 sub4 >chks &&
+		sed "s,^,sub dir/," chks >chks_sub &&
+
+		cat chkm chkms_sub chks_sub >expect &&
+		git ls-files >actual &&
+		test_cmp expect actual
+	)
+'
+
+next_test
+test_expect_success 'make sure each filename changed exactly once in the entire history' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git config log.date relative &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub3 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree pull --prefix="sub dir" ./"sub proj" master &&
+
+		test_write_lines main1 main2 >chkm &&
+		test_write_lines sub1 sub2 sub3 sub4 >chks &&
+		test_write_lines main-sub1 main-sub2 main-sub3 main-sub4 >chkms &&
+		sed "s,^,sub dir/," chkms >chkms_sub &&
+
+		# main-sub?? and /"sub dir"/main-sub?? both change, because those are the
+		# changes that were split into their own history.  And "sub dir"/sub?? never
+		# change, since they were *only* changed in the subtree branch.
+		git log --name-only --pretty=format:"" >log &&
+		sort <log >sorted-log &&
+		sed "/^$/ d" sorted-log >actual &&
+
+		cat chkms chkm chks chkms_sub >expect-unsorted &&
+		sort expect-unsorted >expect &&
+		test_cmp expect actual
+	)
+'
+
+next_test
+test_expect_success 'make sure the --rejoin commits never make it into subproj' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub3 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree pull --prefix="sub dir" ./"sub proj" master &&
+		check_equal "$(git log --pretty=format:"%s" HEAD^2 | grep -i split)" ""
+	)
+'
+
+next_test
+test_expect_success 'make sure no "git subtree" tagged commits make it into subproj' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub3 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		 git merge FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub4 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --annotate="*" --branch subproj-br --rejoin
+	) &&
+	(
+		cd "$subtree_test_count/sub proj" &&
+		git fetch .. subproj-br &&
+		git merge FETCH_HEAD
+	) &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree pull --prefix="sub dir" ./"sub proj" master &&
+
+		# They are meaningless to subproj since one side of the merge refers to the mainline
+		check_equal "$(git log --pretty=format:"%s%n%b" HEAD^2 | grep "git-subtree.*:")" ""
+	)
+'
+
+#
+# A new set of tests
+#
+
+next_test
+test_expect_success 'make sure "git subtree split" find the correct parent' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git branch subproj-ref FETCH_HEAD &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --branch subproj-br &&
+
+		# at this point, the new commit parent should be subproj-ref, if it is
+		# not, something went wrong (the "newparent" of "master~" commit should
+		# have been sub2, but it was not, because its cache was not set to
+		# itself)
+		check_equal "$(git log --pretty=format:%P -1 subproj-br)" "$(git rev-parse subproj-ref)"
+	)
+'
+
+next_test
+test_expect_success 'split a new subtree without --onto option' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --branch subproj-br
+	) &&
+	mkdir "$subtree_test_count"/"sub dir2" &&
+	test_create_commit "$subtree_test_count" "sub dir2"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+
+		# also test that we still can split out an entirely new subtree
+		# if the parent of the first commit in the tree is not empty,
+		# then the new subtree has accidentally been attached to something
+		git subtree split --prefix="sub dir2" --branch subproj2-br &&
+		check_equal "$(git log --pretty=format:%P -1 subproj2-br)" ""
+	)
+'
+
+next_test
+test_expect_success 'verify one file change per commit' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git branch sub1 FETCH_HEAD &&
+		git subtree add --prefix="sub dir" sub1
+	) &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir" --branch subproj-br
+	) &&
+	mkdir "$subtree_test_count"/"sub dir2" &&
+	test_create_commit "$subtree_test_count" "sub dir2"/main-sub2 &&
+	(
+		cd "$subtree_test_count" &&
+		git subtree split --prefix="sub dir2" --branch subproj2-br &&
+
+		x= &&
+		git log --pretty=format:"commit: %H" | join_commits |
+		(
+			while read commit a b; do
+				test_debug "echo Verifying commit $commit"
+				test_debug "echo a: $a"
+				test_debug "echo b: $b"
+				check_equal "$b" ""
+				x=1
+			done
+			check_equal "$x" 1
+		)
+	)
+'
+
+next_test
+test_expect_success 'push split to subproj' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	subtree_test_create_repo "$subtree_test_count/sub proj" &&
+	test_create_commit "$subtree_test_count" main1 &&
+	test_create_commit "$subtree_test_count/sub proj" sub1 &&
+	(
+		cd "$subtree_test_count" &&
+		git fetch ./"sub proj" master &&
+		git subtree add --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub1 &&
+	test_create_commit "$subtree_test_count" main2 &&
+	test_create_commit "$subtree_test_count/sub proj" sub2 &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub2 &&
+	(
+		cd $subtree_test_count/"sub proj" &&
+                git branch sub-branch-1 &&
+                cd .. &&
+		git fetch ./"sub proj" master &&
+		git subtree merge --prefix="sub dir" FETCH_HEAD
+	) &&
+	test_create_commit "$subtree_test_count" "sub dir"/main-sub3 &&
+        (
+		cd "$subtree_test_count" &&
+	        git subtree push ./"sub proj" --prefix "sub dir" sub-branch-1 &&
+                cd ./"sub proj" &&
+                git checkout sub-branch-1 &&
+         	check_equal "$(last_commit_message)" "sub dir/main-sub3"
+	)
+'
+
+#
+# This test covers 2 cases in subtree split copy_or_skip code
+# 1) Merges where one parent is a superset of the changes of the other
+#    parent regarding changes to the subtree, in this case the merge
+#    commit should be copied
+# 2) Merges where only one parent operate on the subtree, and the merge
+#    commit should be skipped
+#
+# (1) is checked by ensuring subtree_tip is a descendent of subtree_branch
+# (2) should have a check added (not_a_subtree_change shouldn't be present
+#     on the produced subtree)
+#
+# Other related cases which are not tested (or currently handled correctly)
+# - Case (1) where there are more than 2 parents, it will sometimes correctly copy
+#   the merge, and sometimes not
+# - Merge commit where both parents have same tree as the merge, currently
+#   will always be skipped, even if they reached that state via different
+#   set of commits.
+#
+
+next_test
+test_expect_success 'subtree descendant check' '
+	subtree_test_create_repo "$subtree_test_count" &&
+	test_create_commit "$subtree_test_count" folder_subtree/a &&
+	(
+		cd "$subtree_test_count" &&
+		git branch branch
+	) &&
+	test_create_commit "$subtree_test_count" folder_subtree/0 &&
+	test_create_commit "$subtree_test_count" folder_subtree/b &&
+	cherry=$(cd "$subtree_test_count"; git rev-parse HEAD) &&
+	(
+		cd "$subtree_test_count" &&
+		git checkout branch
+	) &&
+	test_create_commit "$subtree_test_count" commit_on_branch &&
+	(
+		cd "$subtree_test_count" &&
+		git cherry-pick $cherry &&
+		git checkout master &&
+		git merge -m "merge should be kept on subtree" branch &&
+		git branch no_subtree_work_branch
+	) &&
+	test_create_commit "$subtree_test_count" folder_subtree/d &&
+	(
+		cd "$subtree_test_count" &&
+		git checkout no_subtree_work_branch
+	) &&
+	test_create_commit "$subtree_test_count" not_a_subtree_change &&
+	(
+		cd "$subtree_test_count" &&
+		git checkout master &&
+		git merge -m "merge should be skipped on subtree" no_subtree_work_branch &&
+
+		git subtree split --prefix folder_subtree/ --branch subtree_tip master &&
+		git subtree split --prefix folder_subtree/ --branch subtree_branch branch &&
+		check_equal $(git rev-list --count subtree_tip..subtree_branch) 0
+	)
+'
+
+test_done
diff --git a/third_party/git/contrib/subtree/todo b/third_party/git/contrib/subtree/todo
new file mode 100644
index 000000000000..0d0e77765175
--- /dev/null
+++ b/third_party/git/contrib/subtree/todo
@@ -0,0 +1,48 @@
+
+	delete tempdir
+
+	'git subtree rejoin' option to do the same as --rejoin, eg. after a
+	  rebase
+
+	--prefix doesn't force the subtree correctly in merge/pull:
+	"-s subtree" should be given an explicit subtree option?
+		There doesn't seem to be a way to do this.  We'd have to
+		patch git-merge-subtree.  Ugh.
+		(but we could avoid this problem by generating squashes with
+		exactly the right subtree structure, rather than using
+		subtree merge...)
+
+	add a 'log' subcommand to see what's new in a subtree?
+
+	add to-submodule and from-submodule commands
+
+	automated tests for --squash stuff
+
+	"add" command non-obviously requires a commitid; would be easier if
+		it had a "pull" sort of mode instead
+
+	"pull" and "merge" commands should fail if you've never merged
+		that --prefix before
+		
+	docs should provide an example of "add"
+	
+	note that the initial split doesn't *have* to have a commitid
+		specified... that's just an optimization
+
+	if you try to add (or maybe merge?) with an invalid commitid, you
+		get a misleading "prefix must end with /" message from
+		one of the other git tools that git-subtree calls.  Should
+		detect this situation and print the *real* problem.
+	
+	"pull --squash" should do fetch-synthesize-merge, but instead just
+		does "pull" directly, which doesn't work at all.
+
+	make a 'force-update' that does what 'add' does even if the subtree
+		already exists.  That way we can help people who imported
+		subtrees "incorrectly" (eg. by just copying in the files) in
+		the past.
+
+	guess --prefix automatically if possible based on pwd
+
+	make a 'git subtree grafts' that automatically expands --squash'd
+		commits so you can see the full history if you want it.