[PATCH] stash: print the correct usage on "git stash [push] --invalid-option"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change the usage message emitted by "git stash --invalid-option" to
emit usage information for "git stash" in general, and not just for
the "push" command.

That we emitted the usage for just "push" in the case of the
subcommand not being explicitly specified was an unintentional
side-effect of how it was implemented. When it was converted to C in
d553f538b8a (stash: convert push to builtin, 2019-02-25) the pattern
of having per-subcommand usage information was rightly continued. The
Git-stash.sh shellscript did not have that, and always printed the
equivalent of "git_stash_usage".

But in doing so the case of push being implicit and explicit was
conflated. A variable was added to track this in 8c3713cede7 (stash:
eliminate crude option parsing, 2020-02-17), but it did not update the
usage output accordingly. Let's do that.

This still leaves e.g. "git stash push -h" emitting the
"git_stash_usage" output, instead of "git_stash_push_usage". That
should be fixed, but is a much deeper misbehavior in parse_options()
not being aware of subcommands at all. I.e. in how
PARSE_OPT_KEEP_UNKNOWN and PARSE_OPT_NO_INTERNAL_HELP combine in
commands such as "git stash".

Perhaps PARSE_OPT_KEEP_UNKNOWN should imply
PARSE_OPT_NO_INTERNAL_HELP, or better yet parse_options() should be
extended to fully handle these subcommand cases that we handle
manually in "git stash", "git commit-graph", "git multi-pack-index"
etc. All of those musings would be a much bigger change than this
isolated fix though, so let's leave that for some other time.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/stash.c  |  1 +
 t/t3903-stash.sh | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/builtin/stash.c b/builtin/stash.c
index 8f42360ca91..cf62c3b3cd8 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -1608,6 +1608,7 @@ static int push_stash(int argc, const char **argv, const char *prefix,
 	if (argc) {
 		force_assume = !strcmp(argv[0], "-p");
 		argc = parse_options(argc, argv, prefix, options,
+				     push_assumed ? git_stash_usage :
 				     git_stash_push_usage,
 				     PARSE_OPT_KEEP_DASHDASH);
 	}
diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
index 873aa56e359..ba9582bdee5 100755
--- a/t/t3903-stash.sh
+++ b/t/t3903-stash.sh
@@ -10,6 +10,17 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
+test_expect_success 'usage' '
+	test_expect_code 129 git stash -h >out &&
+	grep "or: git stash" out &&
+
+	test_expect_code 129 git stash --invalid-option >out 2>err &&
+	grep "or: git stash" err &&
+
+	test_expect_code 129 git stash push --invalid-option >out 2>err &&
+	! grep "or: git stash" err
+'
+
 diff_cmp () {
 	for i in "$1" "$2"
 	do
-- 
2.33.0.807.gf14ecf9c2e9