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, 19 insertions, 6 deletions

diff --git a/third_party/git/Documentation/git-diff.txt b/third_party/git/Documentation/git-diff.txt
index 72179d993c..727f24d16e 100644
--- a/third_party/git/Documentation/git-diff.txt
+++ b/third_party/git/Documentation/git-diff.txt
@@ -11,15 +11,17 @@ SYNOPSIS
 [verse]
 'git diff' [<options>] [<commit>] [--] [<path>...]
 'git diff' [<options>] --cached [<commit>] [--] [<path>...]
-'git diff' [<options>] <commit> <commit> [--] [<path>...]
+'git diff' [<options>] <commit> [<commit>...] <commit> [--] [<path>...]
+'git diff' [<options>] <commit>...<commit> [--] [<path>...]
 'git diff' [<options>] <blob> <blob>
 'git diff' [<options>] --no-index [--] <path> <path>
 
 DESCRIPTION
 -----------
 Show changes between the working tree and the index or a tree, changes
-between the index and a tree, changes between two trees, changes between
-two blob objects, or changes between two files on disk.
+between the index and a tree, changes between two trees, changes resulting
+from a merge, changes between two blob objects, or changes between two
+files on disk.
 
 'git diff' [<options>] [--] [<path>...]::
 
@@ -36,7 +38,7 @@ two blob objects, or changes between two files on disk.
 	running the command in a working tree controlled by Git and
 	at least one of the paths points outside the working tree,
 	or when running the command outside a working tree
-	controlled by Git.
+	controlled by Git. This form implies `--exit-code`.
 
 'git diff' [<options>] --cached [<commit>] [--] [<path>...]::
 
@@ -61,9 +63,19 @@ two blob objects, or changes between two files on disk.
 	This is to view the changes between two arbitrary
 	<commit>.
 
+'git diff' [<options>] <commit> <commit>... <commit> [--] [<path>...]::
+
+	This form is to view the results of a merge commit.  The first
+	listed <commit> must be the merge itself; the remaining two or
+	more commits should be its parents.  A convenient way to produce
+	the desired set of revisions is to use the {caret}@ suffix.
+	For instance, if `master` names a merge commit, `git diff master
+	master^@` gives the same combined diff as `git show master`.
+
 'git diff' [<options>] <commit>..<commit> [--] [<path>...]::
 
-	This is synonymous to the previous form.  If <commit> on
+	This is synonymous to the earlier form (without the "..") for
+	viewing the changes between two arbitrary <commit>.  If <commit> on
 	one side is omitted, it will have the same effect as
 	using HEAD instead.
 
@@ -196,7 +208,8 @@ linkgit:git-difftool[1],
 linkgit:git-log[1],
 linkgit:gitdiffcore[7],
 linkgit:git-format-patch[1],
-linkgit:git-apply[1]
+linkgit:git-apply[1],
+linkgit:git-show[1]
 
 GIT
 ---