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

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

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+Git 2.14 Release Notes
+======================
+
+Backward compatibility notes and other notable changes.
+
+ * Use of an empty string as a pathspec element that is used for
+   'everything matches' is still warned and Git asks users to use a
+   more explicit '.' for that instead.  The hope is that existing
+   users will not mind this change, and eventually the warning can be
+   turned into a hard error, upgrading the deprecation into removal of
+   this (mis)feature.  That is not scheduled to happen in the upcoming
+   release (yet).
+
+ * Git now avoids blindly falling back to ".git" when the setup
+   sequence said we are _not_ in Git repository.  A corner case that
+   happens to work right now may be broken by a call to die("BUG").
+   We've tried hard to locate such cases and fixed them, but there
+   might still be cases that need to be addressed--bug reports are
+   greatly appreciated.
+
+ * The experiment to improve the hunk-boundary selection of textual
+   diff output has finished, and the "indent heuristics" has now
+   become the default.
+
+ * Git can now be built with PCRE v2 instead of v1 of the PCRE
+   library. Replace USE_LIBPCRE=YesPlease with USE_LIBPCRE2=YesPlease
+   in existing build scripts to build against the new version.  As the
+   upstream PCRE maintainer has abandoned v1 maintenance for all but
+   the most critical bug fixes, use of v2 is recommended.
+
+
+Updates since v2.13
+-------------------
+
+UI, Workflows & Features
+
+ * The colors in which "git status --short --branch" showed the names
+   of the current branch and its remote-tracking branch are now
+   configurable.
+
+ * "git clone" learned the "--no-tags" option not to fetch all tags
+   initially, and also set up the tagopt not to follow any tags in
+   subsequent fetches.
+
+ * "git archive --format=zip" learned to use zip64 extension when
+   necessary to go beyond the 4GB limit.
+
+ * "git reset" learned "--recurse-submodules" option.
+
+ * "git diff --submodule=diff" now recurses into nested submodules.
+
+ * "git repack" learned to accept the --threads=<n> option and pass it
+   to pack-objects.
+
+ * "git send-email" learned to run sendemail-validate hook to inspect
+   and reject a message before sending it out.
+
+ * There is no good reason why "git fetch $there $sha1" should fail
+   when the $sha1 names an object at the tip of an advertised ref,
+   even when the other side hasn't enabled allowTipSHA1InWant.
+
+ * The "[includeIf "gitdir:$dir"] path=..." mechanism introduced in
+   2.13.0 would canonicalize the path of the gitdir being matched,
+   and did not match e.g. "gitdir:~/work/*" against a repo in
+   "~/work/main" if "~/work" was a symlink to "/mnt/storage/work".
+   Now we match both the resolved canonical path and what "pwd" would
+   show. The include will happen if either one matches.
+
+ * The "indent" heuristics is now the default in "diff". The
+   diff.indentHeuristic configuration variable can be set to "false"
+   for those who do not want it.
+
+ * Many commands learned to pay attention to submodule.recurse
+   configuration.
+
+ * The convention for a command line is to follow "git cmdname
+   --options" with revisions followed by an optional "--"
+   disambiguator and then finally pathspecs.  When "--" is not there,
+   we make sure early ones are all interpretable as revs (and do not
+   look like paths) and later ones are the other way around.  A
+   pathspec with "magic" (e.g. ":/p/a/t/h" that matches p/a/t/h from
+   the top-level of the working tree, no matter what subdirectory you
+   are working from) are conservatively judged as "not a path", which
+   required disambiguation more often.  The command line parser
+   learned to say "it's a pathspec" a bit more often when the syntax
+   looks like so.
+
+ * Update "perl-compatible regular expression" support to enable JIT
+   and also allow linking with the newer PCRE v2 library.
+
+ * "filter-branch" learned a pseudo filter "--setup" that can be used
+   to define common functions/variables that can be used by other
+   filters.
+
+ * Using "git add d/i/r" when d/i/r is the top of the working tree of
+   a separate repository would create a gitlink in the index, which
+   would appear as a not-quite-initialized submodule to others.  We
+   learned to give warnings when this happens.
+
+ * "git status" learned to optionally give how many stash entries there
+   are in its output.
+
+ * "git status" has long shown essentially the same message as "git
+   commit"; the message it gives while preparing for the root commit,
+   i.e. "Initial commit", was hard to understand for some new users.
+   Now it says "No commits yet" to stress more on the current status
+   (rather than the commit the user is preparing for, which is more in
+   line with the focus of "git commit").
+
+ * "git send-email" now has --batch-size and --relogin-delay options
+    which can be used to overcome limitations on SMTP servers that
+    restrict on how many of e-mails can be sent in a single session.
+
+ * An old message shown in the commit log template was removed, as it
+   has outlived its usefulness.
+
+ * "git pull --rebase --recurse-submodules" learns to rebase the
+   branch in the submodules to an updated base.
+
+ * "git log" learned -P as a synonym for --perl-regexp, "git grep"
+   already had such a synonym.
+
+ * "git log" didn't understand --regexp-ignore-case when combined with
+   --perl-regexp. This has been fixed.
+
+Performance, Internal Implementation, Development Support etc.
+
+ * The default packed-git limit value has been raised on larger
+   platforms to save "git fetch" from a (recoverable) failure while
+   "gc" is running in parallel.
+
+ * Code to update the cache-tree has been tightened so that we won't
+   accidentally write out any 0{40} entry in the tree object.
+
+ * Attempt to allow us notice "fishy" situation where we fail to
+   remove the temporary directory used during the test.
+
+ * Travis CI gained a task to format the documentation with both
+   AsciiDoc and AsciiDoctor.
+
+ * Some platforms have ulong that is smaller than time_t, and our
+   historical use of ulong for timestamp would mean they cannot
+   represent some timestamp that the platform allows.  Invent a
+   separate and dedicated timestamp_t (so that we can distingiuish
+   timestamps and a vanilla ulongs, which along is already a good
+   move), and then declare uintmax_t is the type to be used as the
+   timestamp_t.
+
+ * We can trigger Windows auto-build tester (credits: Dscho &
+   Microsoft) from our existing Travis CI tester now.
+
+ * Conversion from uchar[20] to struct object_id continues.
+
+ * Simplify parse_pathspec() codepath and stop it from looking at the
+   default in-core index.
+
+ * Add perf-test for wildmatch.
+
+ * Code from "conversion using external process" codepath has been
+   extracted to a separate sub-process.[ch] module.
+
+ * When "git checkout", "git merge", etc. manipulates the in-core
+   index, various pieces of information in the index extensions are
+   discarded from the original state, as it is usually not the case
+   that they are kept up-to-date and in-sync with the operation on the
+   main index.  The untracked cache extension is copied across these
+   operations now, which would speed up "git status" (as long as the
+   cache is properly invalidated).
+
+ * The internal implementation of "git grep" has seen some clean-up.
+
+ * Update the C style recommendation for notes for translators, as
+   recent versions of gettext tools can work with our style of
+   multi-line comments.
+
+ * The implementation of "ref" API around the "packed refs" have been
+   cleaned up, in preparation for further changes.
+
+ * The internal logic used in "git blame" has been libified to make it
+   easier to use by cgit.
+
+ * Our code often opens a path to an optional file, to work on its
+   contents when we can successfully open it.  We can ignore a failure
+   to open if such an optional file does not exist, but we do want to
+   report a failure in opening for other reasons (e.g. we got an I/O
+   error, or the file is there, but we lack the permission to open).
+
+   The exact errors we need to ignore are ENOENT (obviously) and
+   ENOTDIR (less obvious).  Instead of repeating comparison of errno
+   with these two constants, introduce a helper function to do so.
+
+ * We often try to open a file for reading whose existence is
+   optional, and silently ignore errors from open/fopen; report such
+   errors if they are not due to missing files.
+
+ * When an existing repository is used for t/perf testing, we first
+   create bit-for-bit copy of it, which may grab a transient state of
+   the repository and freeze it into the repository used for testing,
+   which then may cause Git operations to fail.  Single out "the index
+   being locked" case and forcibly drop the lock from the copy.
+
+ * Three instances of the same helper function have been consolidated
+   to one.
+
+ * "fast-import" uses a default pack chain depth that is consistent
+   with other parts of the system.
+
+ * A new test to show the interaction between the pattern [^a-z]
+   (which matches '/') and a slash in a path has been added.  The
+   pattern should not match the slash with "pathmatch", but should
+   with "wildmatch".
+
+ * The 'diff-highlight' program (in contrib/) has been restructured
+   for easier reuse by an external project 'diff-so-fancy'.
+
+ * A common pattern to free a piece of memory and assign NULL to the
+   pointer that used to point at it has been replaced with a new
+   FREE_AND_NULL() macro.
+
+ * Traditionally, the default die() routine had a code to prevent it
+   from getting called multiple times, which interacted badly when a
+   threaded program used it (one downside is that the real error may
+   be hidden and instead the only error message given to the user may
+   end up being "die recursion detected", which is not very useful).
+
+ * Introduce a "repository" object to eventually make it easier to
+   work in multiple repositories (the primary focus is to work with
+   the superproject and its submodules) in a single process.
+
+ * Optimize "what are the object names already taken in an alternate
+   object database?" query that is used to derive the length of prefix
+   an object name is uniquely abbreviated to.
+
+ * The hashmap API has been updated so that data to customize the
+   behaviour of the comparison function can be specified at the time a
+   hashmap is initialized.
+
+ * The "collision detecting" SHA-1 implementation shipped with 2.13 is
+   now integrated into git.git as a submodule (the first submodule to
+   ship with git.git). Clone git.git with --recurse-submodules to get
+   it. For now a non-submodule copy of the same code is also shipped
+   as part of the tree.
+
+ * A recent update made it easier to use "-fsanitize=" option while
+   compiling but supported only one sanitize option.  Allow more than
+   one to be combined, joined with a comma, like "make SANITIZE=foo,bar".
+
+ * Use "p4 -G" to make "p4 changes" output more Python-friendly
+   to parse.
+
+ * We started using "%" PRItime, imitating "%" PRIuMAX and friends, as
+   a way to format the internal timestamp value, but this does not
+   play well with gettext(1) i18n framework, and causes "make pot"
+   that is run by the l10n coordinator to create a broken po/git.pot
+   file.  This is a possible workaround for that problem.
+
+ * It turns out that Cygwin also needs the fopen() wrapper that
+   returns failure when a directory is opened for reading.
+
+Also contains various documentation updates and code clean-ups.
+
+
+Fixes since v2.13
+-----------------
+
+Unless otherwise noted, all the fixes since v2.13 in the maintenance
+track are contained in this release (see the maintenance releases'
+notes for details).
+
+ * "git gc" did not interact well with "git worktree"-managed
+   per-worktree refs.
+
+ * "git cherry-pick" and other uses of the sequencer machinery
+   mishandled a trailer block whose last line is an incomplete line.
+   This has been fixed so that an additional sign-off etc. are added
+   after completing the existing incomplete line.
+
+ * The codepath in "git am" that is used when running "git rebase"
+   leaked memory held for the log message of the commits being rebased.
+
+ * "git clone --config var=val" is a way to populate the
+   per-repository configuration file of the new repository, but it did
+   not work well when val is an empty string.  This has been fixed.
+
+ * Setting "log.decorate=false" in the configuration file did not take
+   effect in v2.13, which has been corrected.
+
+ * A few codepaths in "checkout" and "am" working on an unborn branch
+   tried to access an uninitialized piece of memory.
+
+ * The Web interface to gmane news archive is long gone, even though
+   the articles are still accessible via NTTP.  Replace the links with
+   ones to public-inbox.org.  Because their message identification is
+   based on the actual message-id, it is likely that it will be easier
+   to migrate away from it if/when necessary.
+
+ * The receive-pack program now makes sure that the push certificate
+   records the same set of push options used for pushing.
+
+ * Tests have been updated to pass under GETTEXT_POISON (a mechanism
+   to ensure that output strings that should not be translated are
+   not translated by mistake), and TravisCI is told to run them.
+
+ * "git checkout --recurse-submodules" did not quite work with a
+   submodule that itself has submodules.
+
+ * "pack-objects" can stream a slice of an existing packfile out when
+   the pack bitmap can tell that the reachable objects are all needed
+   in the output, without inspecting individual objects.  This
+   strategy however would not work well when "--local" and other
+   options are in use, and need to be disabled.
+
+ * Fix memory leaks pointed out by Coverity (and people).
+
+ * "git read-tree -m" (no tree-ish) gave a nonsense suggestion "use
+   --empty if you want to clear the index".  With "-m", such a request
+   will still fail anyway, as you'd need to name at least one tree-ish
+   to be merged.
+
+ * Make sure our tests would pass when the sources are checked out
+   with "platform native" line ending convention by default on
+   Windows.  Some "text" files out tests use and the test scripts
+   themselves that are meant to be run with /bin/sh, ought to be
+   checked out with eol=LF even on Windows.
+
+ * Introduce the BUG() macro to improve die("BUG: ...").
+
+ * Clarify documentation for include.path and includeIf.<condition>.path
+   configuration variables.
+
+ * Git sometimes gives an advice in a rhetorical question that does
+   not require an answer, which can confuse new users and non native
+   speakers.  Attempt to rephrase them.
+
+ * A few http:// links that are redirected to https:// in the
+   documentation have been updated to https:// links.
+
+ * "git for-each-ref --format=..." with %(HEAD) in the format used to
+   resolve the HEAD symref as many times as it had processed refs,
+   which was wasteful, and "git branch" shared the same problem.
+
+ * Regression fix to topic recently merged to 'master'.
+
+ * The shell completion script (in contrib/) learned "git stash" has
+   a new "push" subcommand.
+
+ * "git interpret-trailers", when used as GIT_EDITOR for "git commit
+   -v", looked for and appended to a trailer block at the very end,
+   i.e. at the end of the "diff" output.  The command has been
+   corrected to pay attention to the cut-mark line "commit -v" adds to
+   the buffer---the real trailer block should appear just before it.
+
+ * A test allowed both "git push" and "git receive-pack" on the other
+   end write their traces into the same file.  This is OK on platforms
+   that allows atomically appending to a file opened with O_APPEND,
+   but on other platforms led to a mangled output, causing
+   intermittent test failures.  This has been fixed by disabling
+   traces from "receive-pack" in the test.
+
+ * Tag objects, which are not reachable from any ref, that point at
+   missing objects were mishandled by "git gc" and friends (they
+   should silently be ignored instead)
+
+ * "git describe --contains" penalized light-weight tags so much that
+   they were almost never considered.  Instead, give them about the
+   same chance to be considered as an annotated tag that is the same
+   age as the underlying commit would.
+
+ * The "run-command" API implementation has been made more robust
+   against dead-locking in a threaded environment.
+
+ * A recent update to t5545-push-options.sh started skipping all the
+   tests in the script when a web server testing is disabled or
+   unavailable, not just the ones that require a web server.  Non HTTP
+   tests have been salvaged to always run in this script.
+
+ * "git send-email" now uses Net::SMTP::SSL, which is obsolete, only
+   when needed.  Recent versions of Net::SMTP can do TLS natively.
+
+ * "foo\bar\baz" in "git fetch foo\bar\baz", even though there is no
+   slashes in it, cannot be a nickname for a remote on Windows, as
+   that is likely to be a pathname on a local filesystem.
+
+ * "git clean -d" used to clean directories that has ignored files,
+   even though the command should not lose ignored ones without "-x".
+   "git status --ignored"  did not list ignored and untracked files
+   without "-uall".  These have been corrected.
+
+ * The result from "git diff" that compares two blobs, e.g. "git diff
+   $commit1:$path $commit2:$path", used to be shown with the full
+   object name as given on the command line, but it is more natural to
+   use the $path in the output and use it to look up .gitattributes.
+
+ * The "collision detecting" SHA-1 implementation shipped with 2.13
+   was quite broken on some big-endian platforms and/or platforms that
+   do not like unaligned fetches.  Update to the upstream code which
+   has already fixed these issues.
+
+ * "git am -h" triggered a BUG().
+
+ * The interaction of "url.*.insteadOf" and custom URL scheme's
+   whitelisting is now documented better.
+
+ * The timestamp of the index file is now taken after the file is
+   closed, to help Windows, on which a stale timestamp is reported by
+   fstat() on a file that is opened for writing and data was written
+   but not yet closed.
+
+ * "git pull --rebase --autostash" didn't auto-stash when the local history
+   fast-forwards to the upstream.
+
+ * A flaky test has been corrected.
+
+ * "git $cmd -h" for builtin commands calls the implementation of the
+   command (i.e. cmd_$cmd() function) without doing any repository
+   set-up, and the commands that expect RUN_SETUP is done by the Git
+   potty needs to be prepared to show the help text without barfing.
+   (merge d691551192 jk/consistent-h later to maint).
+
+ * Help contributors that visit us at GitHub.
+
+ * "git stash push <pathspec>" did not work from a subdirectory at all.
+   Bugfix for a topic in v2.13
+
+ * As there is no portable way to pass timezone information to
+   strftime, some output format from "git log" and friends are
+   impossible to produce.  Teach our own strbuf_addftime to replace %z
+   and %Z with caller-supplied values to help working around this.
+   (merge 6eced3ec5e rs/strbuf-addftime-zZ later to maint).
+
+ * "git mergetool" learned to work around a wrapper MacOS X adds
+   around underlying meld.
+
+ * An example in documentation that does not work in multi worktree
+   configuration has been corrected.
+
+ * The pretty-format specifiers like '%h', '%t', etc. had an
+   optimization that no longer works correctly.  In preparation/hope
+   of getting it correctly implemented, first discard the optimization
+   that is broken.
+
+ * The code to pick up and execute command alias definition from the
+   configuration used to switch to the top of the working tree and
+   then come back when the expanded alias was executed, which was
+   unnecessarilyl complex.  Attempt to simplify the logic by using the
+   early-config mechanism that does not chdir around.
+
+ * Fix configuration codepath to pay proper attention to commondir
+   that is used in multi-worktree situation, and isolate config API
+   into its own header file.
+   (merge dc8441fdb4 bw/config-h later to maint).
+
+ * "git add -p" were updated in 2.12 timeframe to cope with custom
+   core.commentchar but the implementation was buggy and a
+   metacharacter like $ and * did not work.
+
+ * A recent regression in "git rebase -i" has been fixed and tests
+   that would have caught it and others have been added.
+
+ * An unaligned 32-bit access in pack-bitmap code has been corrected.
+
+ * Tighten error checks for invalid "git apply" input.
+
+ * The split index code did not honor core.sharedRepository setting
+   correctly.
+
+ * The Makefile rule in contrib/subtree for building documentation
+   learned to honour USE_ASCIIDOCTOR just like the main documentation
+   set does.
+
+ * Code clean-up to fix possible buffer over-reading.
+
+ * A few tests that tried to verify the contents of push certificates
+   did not use 'git rev-parse' to formulate the line to look for in
+   the certificate correctly.
+
+ * Update the character width tables.
+
+ * After "git branch --move" of the currently checked out branch, the
+   code to walk the reflog of HEAD via "log -g" and friends
+   incorrectly stopped at the reflog entry that records the renaming
+   of the branch.
+
+ * The rewrite of "git branch --list" using for-each-ref's internals
+   that happened in v2.13 regressed its handling of color.branch.local;
+   this has been fixed.
+
+ * The build procedure has been improved to allow building and testing
+   Git with address sanitizer more easily.
+   (merge 425ca6710b jk/build-with-asan later to maint).
+
+ * On Cygwin, similar to Windows, "git push //server/share/repository"
+   ought to mean a repository on a network share that can be accessed
+   locally, but this did not work correctly due to stripping the double
+   slashes at the beginning.
+
+ * The progress meter did not give a useful output when we haven't had
+   0.5 seconds to measure the throughput during the interval.  Instead
+   show the overall throughput rate at the end, which is a much more
+   useful number.
+
+ * Code clean-up, that makes us in sync with Debian by one patch.
+
+ * We run an early part of "git gc" that deals with refs before
+   daemonising (and not under lock) even when running a background
+   auto-gc, which caused multiple gc processes attempting to run the
+   early part at the same time.  This is now prevented by running the
+   early part also under the GC lock.
+
+ * A recent update broke an alias that contained an uppercase letter.
+
+ * Other minor doc, test and build updates and code cleanups.
+   (merge 5053313562 rs/urlmatch-cleanup later to maint).
+   (merge 42c78a216e rs/use-div-round-up later to maint).
+   (merge 5e8d2729ae rs/wt-status-cleanup later to maint).
+   (merge bc9b7e207f as/diff-options-grammofix later to maint).
+   (merge ac05222b31 ah/patch-id-doc later to maint).