Since the preceding commit all sub-commands of "git submodule" have
been dispatched to "git submodule--helper" directly, we therefore
don't need to emit "usage()" if we see "--cached" without the
sub-command being "status" or "summary", we can trust that
parse_options() will spot that and barf on it.

This does change one obscure aspect of undocumented behavior, for
"status" and "summary" we supported these undocumented forms:

    git submodule --cached (status | summary)

As noted in a preceding commit to git-submodule.sh which removed the
"--branch" special-case, this comes down to emergent behavior seen in
5c08dbbdf1a (git-submodule: fix subcommand parser,
2008-01-15). I.e. we wanted to support was for subcommand-less invocations like:

    git submodule --cached

To be synonymous with invocations that explicitly named the "status"
sub-command:

    git submodule status --cached

But we did not intend to mix the two, and allow "--cached" to be an
option to the top-level "submodule" command when the "status" or
"summary" sub-commands were explicitly provided.

Let's remove this undocumented edge case, which makes a subsequent
removal of git-submodule.sh easier to reason about. The test case
added here is duplicated from the existing for-loop, except for the
different and desired handling of "git submodule --cached status".

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
---
 git-submodule.sh           | 15 ++++++++-------
 t/t7400-submodule-basic.sh | 15 +++++++++++++--
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/git-submodule.sh b/git-submodule.sh
index ac2f95c1285..4f8f62ce981 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh

@@ -43,7 +43,14 @@ do
 		quiet=1
 		;;
 	--cached)
-		cached=1
+		if test -z "$command"
+		then
+			cached=1 &&
+			shift &&
+			break
+		else
+			usage
+		fi
 		;;
 	--)
 		break

@@ -69,12 +76,6 @@ then
     fi
 fi
 
-# "--cached" is accepted only by "status" and "summary"
-if test -n "$cached" && test "$command" != status && test "$command" != summary
-then
-	usage
-fi
-
 case "$command" in
 absorbgitdirs)
 	git submodule--helper "$command" --prefix "$wt_prefix" "$@"

diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index b50db3f1031..d8f7d6ee29a 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh

@@ -31,7 +31,7 @@ test_expect_success 'submodule usage: status --' '
 	test_expect_code 1 git submodule --end-of-options
 '
 
-for opt in '--quiet' '--cached'
+for opt in '--quiet'
 do
 	test_expect_success "submodule usage: status $opt" '
 		git submodule $opt &&

@@ -40,6 +40,17 @@ do
 	'
 done
 
+for opt in '--cached'
+do
+	test_expect_success "submodule usage: status $opt" '
+		git submodule $opt &&
+		git submodule status $opt &&
+		test_expect_code 1 git submodule $opt status >out 2>err &&
+		grep "^usage: git submodule" err &&
+		test_must_be_empty out
+	'
+done
+
 test_expect_success 'submodule deinit works on empty repository' '
 	git submodule deinit --all
 '

@@ -576,7 +587,7 @@ test_expect_success 'status should be "modified" after submodule commit' '
 '
 
 test_expect_success 'the --cached sha1 should be rev1' '
-	git submodule --cached status >list &&
+	git submodule status --cached >list &&
 	grep "^+$rev1" list
 '
 

-- 
2.38.0.1091.gf9d18265e59