[PATCH] diff: fix crash with --find-object outside repository

["Michael Montalbo via GitGitGadget" <gitgitgadget@gmail.com>]

From: Michael Montalbo <mmontalbo@gmail.com>

When "git diff --find-object=<oid>" is run outside a git repository,
the option parsing callback eagerly resolves the OID via
repo_get_oid(), which reaches get_main_ref_store() and hits a BUG()
assertion because no repository has been set up.

Check startup_info->have_repository before attempting to resolve the
OID, and return a user-friendly error instead.

Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
---
    diff: fix crash with --find-object outside repository

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2057%2Fmmontalbo%2Ffix-find-object-crash-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2057/mmontalbo/fix-find-object-crash-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/2057

 diff.c                   |  2 ++
 t/t4053-diff-no-index.sh | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/diff.c b/diff.c
index a68ddd2168..8f0f141be7 100644
--- a/diff.c
+++ b/diff.c
@@ -5215,6 +5215,8 @@ 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);
 
diff --git a/t/t4053-diff-no-index.sh b/t/t4053-diff-no-index.sh
index 69599279e9..15076dfe0d 100755
--- a/t/t4053-diff-no-index.sh
+++ b/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 &&

base-commit: 67ad42147a7acc2af6074753ebd03d904476118f
-- 
gitgitgadget