stash: introduce 'git stash store'

save_stash() contains the logic for doing two potentially independent
operations; the first is preparing the stash merge commit, and the
second is updating the stash ref/ reflog accordingly.  While the first
operation is abstracted out into a create_stash() for callers to access
via 'git stash create', the second one is not.  Fix this by factoring
out the logic for storing the stash into a store_stash() that callers
can access via 'git stash store'.

Like create, store is not intended for end user interactive use, but for
callers in other scripts.  We can simplify the logic in the
rebase.autostash feature using this new subcommand.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-stash.txt

@@ -17,6 +17,7 @@ SYNOPSIS
 	     [-u|--include-untracked] [-a|--all] [<message>]]
 'git stash' clear
 'git stash' create [<message>]
+'git stash' store [-m|--message <message>] [-q|--quiet] <commit>
 
 DESCRIPTION
 -----------
@@ -154,6 +155,12 @@ create::
 	This is intended to be useful for scripts.  It is probably not
 	the command you want to use; see "save" above.
 
+store::
+
+	Store a given stash created via 'git stash create' (which is a
+	dangling merge commit) in the stash ref, updating the stash
+	reflog.  This is intended to be useful for scripts.  It is
+	probably not the command you want to use; see "save" above.
 
 DISCUSSION
 ----------

git-stash.sh

@@ -156,6 +156,41 @@ create_stash () {
 	die "$(gettext "Cannot record working tree state")"
 }
 
+store_stash () {
+	while test $# != 0
+	do
+		case "$1" in
+		-m|--message)
+			shift
+			stash_msg="$1"
+			;;
+		-q|--quiet)
+			quiet=t
+			;;
+		*)
+			break
+			;;
+		esac
+		shift
+	done
+	test $# = 1 ||
+	die "$(eval_gettext "\"$dashless store\" requires one <commit> argument")"
+
+	w_commit="$1"
+	if test -z "$stash_msg"
+	then
+		stash_msg="Created via \"git stash store\"."
+	fi
+
+	# Make sure the reflog for stash is kept.
+	: >>"$GIT_DIR/logs/$ref_stash"
+	git update-ref -m "$stash_msg" $ref_stash $w_commit
+	ret=$?
+	test $ret != 0 && test -z $quiet &&
+	die "$(eval_gettext "Cannot update \$ref_stash with \$w_commit")"
+	return $ret
+}
+
 save_stash () {
 	keep_index=
 	patch_mode=
@@ -227,12 +262,8 @@ save_stash () {
 		clear_stash || die "$(gettext "Cannot initialize stash")"
 
 	create_stash "$stash_msg" $untracked
-
-	# Make sure the reflog for stash is kept.
-	: >>"$GIT_DIR/logs/$ref_stash"
-
-	git update-ref -m "$stash_msg" $ref_stash $w_commit ||
-		die "$(gettext "Cannot save the current status")"
+	store_stash -m "$stash_msg" -q $w_commit ||
+	die "$(gettext "Cannot save the current status")"
 	say Saved working directory and index state "$stash_msg"
 
 	if test -z "$patch_mode"
@@ -549,6 +580,10 @@ create)
 	shift
 	create_stash "$*" && echo "$w_commit"
 	;;
+store)
+	shift
+	store_stash "$@"
+	;;
 drop)
 	shift
 	drop_stash "$@"

t/t3903-stash.sh

@@ -637,4 +637,23 @@ test_expect_success 'stash where working directory contains "HEAD" file' '
 	test_cmp output expect
 '
 
+test_expect_success 'store called with invalid commit' '
+	test_must_fail git stash store foo
+'
+
+test_expect_success 'store updates stash ref and reflog' '
+	git stash clear &&
+	git reset --hard &&
+	echo quux >bazzy &&
+	git add bazzy &&
+	STASH_ID=$(git stash create) &&
+	git reset --hard &&
+	! grep quux bazzy &&
+	git stash store -m quuxery $STASH_ID &&
+	test $(cat .git/refs/stash) = $STASH_ID &&
+	grep $STASH_ID .git/logs/refs/stash &&
+	git stash pop &&
+	grep quux bazzy
+'
+
 test_done