merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 46 insertions, 8 deletions

diff --git a/third_party/git/Documentation/git-fast-export.txt b/third_party/git/Documentation/git-fast-export.txt
index cc940eb9ada3..1978dbdc6add 100644
--- a/third_party/git/Documentation/git-fast-export.txt
+++ b/third_party/git/Documentation/git-fast-export.txt
@@ -17,9 +17,9 @@ This program dumps the given revisions in a form suitable to be piped
 into 'git fast-import'.
 
 You can use it as a human-readable bundle replacement (see
-linkgit:git-bundle[1]), or as a kind of an interactive
-'git filter-branch'.
-
+linkgit:git-bundle[1]), or as a format that can be edited before being
+fed to 'git fast-import' in order to do history rewrites (an ability
+relied on by tools like 'git filter-repo').
 
 OPTIONS
 -------
@@ -75,11 +75,20 @@ produced incorrect results if you gave these options.
 	Before processing any input, load the marks specified in
 	<file>.  The input file must exist, must be readable, and
 	must use the same format as produced by --export-marks.
+
+--mark-tags::
+	In addition to labelling blobs and commits with mark ids, also
+	label tags.  This is useful in conjunction with
+	`--export-marks` and `--import-marks`, and is also useful (and
+	necessary) for exporting of nested tags.  It does not hurt
+	other cases and would be the default, but many fast-import
+	frontends are not prepared to accept tags with mark
+	identifiers.
 +
-Any commits that have already been marked will not be exported again.
-If the backend uses a similar --import-marks file, this allows for
-incremental bidirectional exporting of the repository by keeping the
-marks the same across runs.
+Any commits (or tags) that have already been marked will not be
+exported again.  If the backend uses a similar --import-marks file,
+this allows for incremental bidirectional exporting of the repository
+by keeping the marks the same across runs.
 
 --fake-missing-tagger::
 	Some old repositories have tags without a tagger.  The
@@ -110,6 +119,11 @@ marks the same across runs.
 	the shape of the history and stored tree.  See the section on
 	`ANONYMIZING` below.
 
+--anonymize-map=<from>[:<to>]::
+	Convert token `<from>` to `<to>` in the anonymized output. If
+	`<to>` is omitted, map `<from>` to itself (i.e., do not
+	anonymize it). See the section on `ANONYMIZING` below.
+
 --reference-excluded-parents::
 	By default, running a command such as `git fast-export
 	master~5..master` will not include the commit master{tilde}5
@@ -133,7 +147,7 @@ marks the same across runs.
 	Specify how to handle `encoding` header in commit objects.  When
 	asking to 'abort' (which is the default), this program will die
 	when encountering such a commit object.  With 'yes', the commit
-	message will be reencoded into UTF-8.  With 'no', the original
+	message will be re-encoded into UTF-8.  With 'no', the original
 	encoding will be preserved.
 
 --refspec::
@@ -229,6 +243,30 @@ collapse "User 0", "User 1", etc into "User X"). This produces a much
 smaller output, and it is usually easy to quickly confirm that there is
 no private data in the stream.
 
+Reproducing some bugs may require referencing particular commits or
+paths, which becomes challenging after refnames and paths have been
+anonymized. You can ask for a particular token to be left as-is or
+mapped to a new value. For example, if you have a bug which reproduces
+with `git rev-list sensitive -- secret.c`, you can run:
+
+---------------------------------------------------
+$ git fast-export --anonymize --all \
+      --anonymize-map=sensitive:foo \
+      --anonymize-map=secret.c:bar.c \
+      >stream
+---------------------------------------------------
+
+After importing the stream, you can then run `git rev-list foo -- bar.c`
+in the anonymized repository.
+
+Note that paths and refnames are split into tokens at slash boundaries.
+The command above would anonymize `subdir/secret.c` as something like
+`path123/bar.c`; you could then search for `bar.c` in the anonymized
+repository to determine the final pathname.
+
+To make referencing the final pathname simpler, you can map each path
+component; so if you also anonymize `subdir` to `publicdir`, then the
+final pathname would be `publicdir/bar.c`.
 
 LIMITATIONS
 -----------