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, 33 insertions, 14 deletions

diff --git a/third_party/git/Documentation/merge-options.txt b/third_party/git/Documentation/merge-options.txt
index 79a00d2a4abd..80d4831662c5 100644
--- a/third_party/git/Documentation/merge-options.txt
+++ b/third_party/git/Documentation/merge-options.txt
@@ -34,32 +34,39 @@ set to `no` at the beginning of them.
 
 --cleanup=<mode>::
 	This option determines how the merge message will be cleaned up before
-	commiting. See linkgit:git-commit[1] for more details. In addition, if
+	committing. See linkgit:git-commit[1] for more details. In addition, if
 	the '<mode>' is given a value of `scissors`, scissors will be appended
 	to `MERGE_MSG` before being passed on to the commit machinery in the
 	case of a merge conflict.
 
 --ff::
-	When the merge resolves as a fast-forward, only update the branch
-	pointer, without creating a merge commit.  This is the default
-	behavior.
-
 --no-ff::
-	Create a merge commit even when the merge resolves as a
-	fast-forward.  This is the default behaviour when merging an
-	annotated (and possibly signed) tag that is not stored in
-	its natural place in 'refs/tags/' hierarchy.
-
 --ff-only::
-	Refuse to merge and exit with a non-zero status unless the
-	current `HEAD` is already up to date or the merge can be
-	resolved as a fast-forward.
+	Specifies how a merge is handled when the merged-in history is
+	already a descendant of the current history.  `--ff` is the
+	default unless merging an annotated (and possibly signed) tag
+	that is not stored in its natural place in the `refs/tags/`
+	hierarchy, in which case `--no-ff` is assumed.
++
+With `--ff`, when possible resolve the merge as a fast-forward (only
+update the branch pointer to match the merged branch; do not create a
+merge commit).  When not possible (when the merged-in history is not a
+descendant of the current history), create a merge commit.
++
+With `--no-ff`, create a merge commit in all cases, even when the merge
+could instead be resolved as a fast-forward.
++
+With `--ff-only`, resolve the merge as a fast-forward when possible.
+When not possible, refuse to merge and exit with a non-zero status.
 
 -S[<keyid>]::
 --gpg-sign[=<keyid>]::
+--no-gpg-sign::
 	GPG-sign the resulting merge commit. The `keyid` argument is
 	optional and defaults to the committer identity; if specified,
-	it must be stuck to the option without a space.
+	it must be stuck to the option without a space. `--no-gpg-sign`
+	is useful to countermand both `commit.gpgSign` configuration variable,
+	and earlier `--gpg-sign`.
 
 --log[=<n>]::
 --no-log::
@@ -105,6 +112,10 @@ option can be used to override --squash.
 +
 With --squash, --commit is not allowed, and will fail.
 
+--no-verify::
+	This option bypasses the pre-merge and commit-msg hooks.
+	See also linkgit:githooks[5].
+
 -s <strategy>::
 --strategy=<strategy>::
 	Use the given merge strategy; can be supplied more than
@@ -149,6 +160,14 @@ ifndef::git-pull[]
 
 endif::git-pull[]
 
+--autostash::
+--no-autostash::
+	Automatically create a temporary stash entry before the operation
+	begins, and apply it after the operation ends.  This means
+	that you can run the operation on a dirty worktree.  However, use
+	with care: the final stash application after a successful
+	merge might result in non-trivial conflicts.
+
 --allow-unrelated-histories::
 	By default, `git merge` command refuses to merge histories
 	that do not share a common ancestor.  This option can be