Merge branch 'mm/diff-no-index-find-object'

"git diff --no-index --find-object=<object-name>" outside a
repository of course wouldn't be able to find the object and died
while parsing the command line, which is made to die in a bit more
user-friendly way.

* mm/diff-no-index-find-object:
  diff: fix crash with --find-object outside repository

Author: gitster

diff.c

@@ -5224,6 +5224,8 @@ static int diff_opt_find_object(const struct option *option,
 	struct object_id oid;
 
 	BUG_ON_OPT_NEG(unset);
+	if (!startup_info->have_repository)
+		return error(_("--find-object requires a git repository"));
 	if (repo_get_oid(the_repository, arg, &oid))
 		return error(_("unable to resolve '%s'"), arg);
 

t/t4053-diff-no-index.sh

@@ -76,6 +76,16 @@ test_expect_success 'git diff --no-index executed outside repo gives correct err
 	)
 '
 
+test_expect_success 'git diff --find-object outside repo fails gracefully' '
+	(
+		GIT_CEILING_DIRECTORIES=$TRASH_DIRECTORY/non &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd non/git &&
+		test_must_fail git diff --find-object=abc123 2>err &&
+		test_grep "find-object requires a git repository" err
+	)
+'
+
 test_expect_success 'diff D F and diff F D' '
 	(
 		cd repo &&