rebase: save autostash entry into stash reflog on --quit

In a03b55530a (merge: teach --autostash option, 2020-04-07), the
--autostash option was introduced for `git merge`. Notably, when
`git merge --quit` is run with an autostash entry present, it is saved
into the stash reflog. This is contrasted with the current behaviour of
`git rebase --quit` where the autostash entry is simply just dropped out
of existence.

Adopt the behaviour of `git merge --quit` in `git rebase --quit` and
save the autostash entry into the stash reflog instead of just deleting
it.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rebase.txt

@@ -256,7 +256,8 @@ See also INCOMPATIBLE OPTIONS below.
 --quit::
 	Abort the rebase operation but HEAD is not reset back to the
 	original branch. The index and working tree are also left
-	unchanged as a result.
+	unchanged as a result. If a temporary stash entry was created
+	using --autostash, it will be saved to the stash reflog.
 
 --apply:
 	Use applying strategies to rebase (calling `git-am`

builtin/rebase.c

@@ -1556,6 +1556,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		goto cleanup;
 	}
 	case ACTION_QUIT: {
+		save_autostash(state_dir_path("autostash", &options));
 		if (options.type == REBASE_MERGE) {
 			struct replay_opts replay = REPLAY_OPTS_INIT;
 

t/t3420-rebase-autostash.sh

@@ -184,6 +184,26 @@ testrebase () {
 		git checkout feature-branch
 	'
 
+	test_expect_success "rebase$type: --quit" '
+		test_config rebase.autostash true &&
+		git reset --hard &&
+		git checkout -b rebased-feature-branch feature-branch &&
+		test_when_finished git branch -D rebased-feature-branch &&
+		echo dirty >>file3 &&
+		git diff >expect &&
+		test_must_fail git rebase$type related-onto-branch &&
+		test_path_is_file $dotest/autostash &&
+		test_path_is_missing file3 &&
+		git rebase --quit &&
+		test_when_finished git stash drop &&
+		test_path_is_missing $dotest/autostash &&
+		! grep dirty file3 &&
+		git stash show -p >actual &&
+		test_cmp expect actual &&
+		git reset --hard &&
+		git checkout feature-branch
+	'
+
 	test_expect_success "rebase$type: non-conflicting rebase, conflicting stash" '
 		test_config rebase.autostash true &&
 		git reset --hard &&