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

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

third_party/git/Documentation/git-restore.txt

@@ -8,8 +8,9 @@ git-restore - Restore working tree files
 SYNOPSIS
 --------
 [verse]
-'git restore' [<options>] [--source=<tree>] [--staged] [--worktree] <pathspec>...
-'git restore' (-p|--patch) [<options>] [--source=<tree>] [--staged] [--worktree] [<pathspec>...]
+'git restore' [<options>] [--source=<tree>] [--staged] [--worktree] [--] <pathspec>...
+'git restore' [<options>] [--source=<tree>] [--staged] [--worktree] --pathspec-from-file=<file> [--pathspec-file-nul]
+'git restore' (-p|--patch) [<options>] [--source=<tree>] [--staged] [--worktree] [--] [<pathspec>...]
 
 DESCRIPTION
 -----------
@@ -21,9 +22,8 @@ The command can also be used to restore the content in the index with
 `--staged`, or restore both the working tree and the index with
 `--staged --worktree`.
 
-By default, the restore sources for working tree and the index are the
-index and `HEAD` respectively. `--source` could be used to specify a
-commit as the restore source.
+By default, if `--staged` is given, the contents are restored from `HEAD`,
+otherwise from the index. Use `--source` to restore from a different commit.
 
 See "Reset, restore and revert" in linkgit:git[1] for the differences
 between the three commands.
@@ -38,10 +38,8 @@ OPTIONS
 	tree. It is common to specify the source tree by naming a
 	commit, branch or tag associated with it.
 +
-If not specified, the default restore source for the working tree is
-the index, and the default restore source for the index is
-`HEAD`. When both `--staged` and `--worktree` are specified,
-`--source` must also be specified.
+If not specified, the contents are restored from `HEAD` if `--staged` is
+given, otherwise from the index.
 
 -p::
 --patch::
@@ -106,6 +104,17 @@ in linkgit:git-checkout[1] for details.
 	patterns and unconditionally restores any files in
 	`<pathspec>`.
 
+--recurse-submodules::
+--no-recurse-submodules::
+	If `<pathspec>` names an active submodule and the restore location
+	includes the working tree, the submodule will only be updated if
+	this option is given, in which case its working tree will be
+	restored to the commit recorded in the superproject, and any local
+	modifications overwritten. If nothing (or
+	`--no-recurse-submodules`) is used, submodules working trees will
+	not be updated. Just like linkgit:git-checkout[1], this will detach
+	`HEAD` of the submodule.
+
 --overlay::
 --no-overlay::
 	In overlay mode, the command never removes files when
@@ -113,6 +122,27 @@ in linkgit:git-checkout[1] for details.
 	appear in the `--source` tree are removed, to make them match
 	`<tree>` exactly. The default is no-overlay mode.
 
+--pathspec-from-file=<file>::
+	Pathspec is passed in `<file>` instead of commandline args. If
+	`<file>` is exactly `-` then standard input is used. Pathspec
+	elements are separated by LF or CR/LF. Pathspec elements can be
+	quoted as explained for the configuration variable `core.quotePath`
+	(see linkgit:git-config[1]). See also `--pathspec-file-nul` and
+	global `--literal-pathspecs`.
+
+--pathspec-file-nul::
+	Only meaningful with `--pathspec-from-file`. Pathspec elements are
+	separated with NUL character and all other characters are taken
+	literally (including newlines and quotes).
+
+\--::
+	Do not interpret any more arguments as options.
+
+<pathspec>...::
+	Limits the paths affected by the operation.
++
+For more details, see the 'pathspec' entry in linkgit:gitglossary[7].
+
 EXAMPLES
 --------