[PATCH v3] grep: die gracefully when outside repository

[Kristoffer Haugsbakk <code@xxxxxxxxxxxxxxx>]

Die gracefully when `git grep --no-index` is run outside of a Git
repository and the path is outside the directory tree.

If you are not in a Git repository and say:

    git grep --no-index search ..

You trigger a `BUG`:

    BUG: environment.c:213: git environment hasn't been setup
    Aborted (core dumped)

Because `..` is a valid path which is treated as a pathspec. Then
`pathspec` figures out that it is not in the current directory tree. The
`BUG` is triggered when `pathspec` tries to advise the user about how the
path is not in the current (non-existing) repository.

Reported-by: ks1322 ks1322 <ks1322@xxxxxxxxx>
Helped-by: Junio C Hamano <gitster@xxxxxxxxx>
Signed-off-by: Kristoffer Haugsbakk <code@xxxxxxxxxxxxxxx>
---

Notes (series):
    v2:
    - Initialize `hint_path` after we know that we are in a Git repository
    - Apply Junio's suggestion for the test: https://lore.kernel.org/git/xmqqzg0hf0g8.fsf@gitster.g/
    v3:
    - commit message: correct to “advise” (“advice” is a noun)

 pathspec.c      |  7 ++++++-
 t/t7810-grep.sh | 27 +++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/pathspec.c b/pathspec.c
index 3a3a5724c44..264b4929a55 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -467,7 +467,12 @@ static void init_pathspec_item(struct pathspec_item *item, unsigned flags,
 		match = prefix_path_gently(prefix, prefixlen,
 					   &prefixlen, copyfrom);
 		if (!match) {
-			const char *hint_path = get_git_work_tree();
+			const char *hint_path;
+
+			if (!have_git_dir())
+				die(_("'%s' is outside the directory tree"),
+				    copyfrom);
+			hint_path = get_git_work_tree();
 			if (!hint_path)
 				hint_path = get_git_dir();
 			die(_("%s: '%s' is outside repository at '%s'"), elt,
diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 39d6d713ecb..84838c0fe1b 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -1234,6 +1234,33 @@ test_expect_success 'outside of git repository with fallbackToNoIndex' '
 	)
 '
 
+test_expect_success 'no repository with path outside $cwd' '
+	test_when_finished rm -fr non &&
+	rm -fr non &&
+	mkdir -p non/git/sub non/tig &&
+	(
+		GIT_CEILING_DIRECTORIES="$(pwd)/non" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd non/git &&
+		test_expect_code 128 git grep --no-index search .. 2>error &&
+		grep "is outside the directory tree" error
+	) &&
+	(
+		GIT_CEILING_DIRECTORIES="$(pwd)/non" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd non/git &&
+		test_expect_code 128 git grep --no-index search ../tig 2>error &&
+		grep "is outside the directory tree" error
+	) &&
+	(
+		GIT_CEILING_DIRECTORIES="$(pwd)/non" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd non/git &&
+		test_expect_code 128 git grep --no-index search ../non 2>error &&
+		grep "no such path in the working tree" error
+	)
+'
+
 test_expect_success 'inside git repository but with --no-index' '
 	rm -fr is &&
 	mkdir -p is/git/sub &&
-- 
2.42.0.2.g879ad04204