[PATCH 1/2] upload-pack: fix ambiguous error message

["Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Elijah Newren <newren@gmail.com>

upload-pack.c takes any --shallow-exclude argument(s) from
clone/fetch/etc. and passes them through expand_ref().  If it does not
get back exactly one ref from the call to expand_ref(), it will die with
the following error:

    fatal: git upload-pack: ambiguous deepen-not: %s

Given that the documentation suggests to users that --shallow-exclude
accepts a revision rather than a ref (which will be corrected in a
subsequent commit), users may try to pass a revision.  In such a case,
expand_ref() will return 0 matches, but the error message we print will
be misleading since "ambiguous" suggests there are multiple matches.
Provide a clearer error message for such a case.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 t/t5500-fetch-pack.sh | 7 +++++++
 upload-pack.c         | 6 +++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index 8da8e7fe423..6552da78d19 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -926,6 +926,13 @@ test_expect_success 'fetch exclude tag one' '
 	test_cmp expected actual
 '
 
+test_expect_success 'fetch exclude tag one as revision' '
+	test_when_finished rm -f rev err &&
+	git -C shallow-exclude rev-parse one >rev &&
+	test_must_fail git -C shallow12 fetch --shallow-exclude $(cat rev) origin 2>err &&
+	grep "deepen-not is not a ref:" err
+'
+
 test_expect_success 'fetching deepen' '
 	test_create_repo shallow-deepen &&
 	(
diff --git a/upload-pack.c b/upload-pack.c
index 6d6e0f9f980..640d45295e1 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -1025,10 +1025,14 @@ static int process_deepen_not(const char *line, struct oidset *deepen_not, int *
 {
 	const char *arg;
 	if (skip_prefix(line, "deepen-not ", &arg)) {
+		int cnt;
 		char *ref = NULL;
 		struct object_id oid;
-		if (expand_ref(the_repository, arg, strlen(arg), &oid, &ref) != 1)
+		cnt = expand_ref(the_repository, arg, strlen(arg), &oid, &ref);
+		if (cnt > 1)
 			die("git upload-pack: ambiguous deepen-not: %s", line);
+		if (cnt < 1)
+			die("git upload-pack: deepen-not is not a ref: %s", line);
 		oidset_insert(deepen_not, &oid);
 		free(ref);
 		*deepen_rev_list = 1;
-- 
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