pull --rebase: add --[no-]autostash flag

If rebase.autoStash configuration variable is set, there is no way to
override it for "git pull --rebase" from the command line.

Teach "git pull --rebase" the --[no-]autostash command line flag which
overrides the current value of rebase.autoStash, if set. As "git rebase"
understands the --[no-]autostash option, it's just a matter of passing
the option to underlying "git rebase" when "git pull --rebase" is called.

Helped-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Paul Tan <pyokagan@gmail.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Mehul Jain <mehul.jain2029@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-pull.txt b/Documentation/git-pull.txt
index a62a2a6..d033b25 100644
--- a/Documentation/git-pull.txt
+++ b/Documentation/git-pull.txt
@@ -128,6 +128,15 @@
 --no-rebase::
 	Override earlier --rebase.
 
+--autostash::
+--no-autostash::
+	Before starting rebase, stash local modifications away (see
+	linkgit:git-stash[1]) if needed, and apply the stash when
+	done. `--no-autostash` is useful to override the `rebase.autoStash`
+	configuration variable (see linkgit:git-config[1]).
++
+This option is only valid when "--rebase" is used.
+
 Options related to fetching
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~