[Outreachy PATCH v4 3/3] t0012: catch builtins that keep NO_PARSEOPT after conversion

[Tanga Joris <tangajoris@gmail.com>]

When a builtin is converted to parse-options, the NO_PARSEOPT flag in
git.c has to be removed by hand. No test checks this. The previous
commit removes the flag from four builtins where it was left behind.

Add a test that runs "git <cmd> --git-completion-helper" for every
builtin left out of "git --list-cmds=parseopt". The test fails if the
command prints an option starting with "--". Without the previous
commit, it fails for diff-pairs, fast-import and patch-id.

The test skips diff, diff-files, diff-index, diff-tree and rev-list,
because they print the diff options. It also skips rev-parse, because
it prints the argument back. It does not catch var, because var only
has short options (like -l) and the helper only lists long options.

Suggested-by: Kaartic Sivaraam <kaartic.sivaraam@gmail.com>
Signed-off-by: Tanga Joris <tangajoris@gmail.com>
---
Kaartic, I put your test in a separate patch for now, so it is easy to
find. I'm happy to squash it into 2/3 if you prefer it there.

 t/t0012-help.sh | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/t/t0012-help.sh b/t/t0012-help.sh
index b0a3fdbbbc..41197c67e2 100755
--- a/t/t0012-help.sh
+++ b/t/t0012-help.sh
@@ -267,4 +267,29 @@ do
 	'
 done <builtins
 
+test_expect_success 'generate list of builtins without parse-options' '
+	git --list-cmds=parseopt >parseopt &&
+	tr " " "\n" <parseopt | sort >sorted-parseopt &&
+	sort builtins >sorted-builtins &&
+	comm -23 sorted-builtins sorted-parseopt >no-parseopt
+'
+
+while read builtin
+do
+	case "$builtin" in
+	# these answer with the diff options
+	diff|diff-files|diff-index|diff-tree|rev-list)
+		continue ;;
+	# rev-parse prints unknown arguments back
+	rev-parse)
+		continue ;;
+	esac
+
+	test_expect_success "$builtin does not answer --git-completion-helper" '
+		test_might_fail git $builtin --git-completion-helper \
+			</dev/null >output 2>/dev/null &&
+		test_grep ! "^--" output
+	'
+done <no-parseopt
+
 test_done
-- 
2.43.0