[PATCH v2 1/1] pathspec: warn for a no-glob entry that contains `**`

["Σταύρος Ντέντος" <stdedos@gmail.com>]

From: Stavros Ntentos <133706+stdedos@users.noreply.github.com>

If a pathspec given that contains `**`, chances are that someone is
naively expecting that it will do what the manual has told him
(i.e. that `**` will match 0-or-more directories).

However, without an explicit `:(glob)` magic, that will fall out the sky:
the two `**` will merge into one star, which surrounded by slashes, will
match any directory name.

These changes attempt to bring awareness to this issue.

Signed-off-by: Stavros Ntentos <133706+stdedos@users.noreply.github.com>
---
 pathspec.c                 | 13 +++++++++++++
 pathspec.h                 |  1 +
 t/t6130-pathspec-noglob.sh | 13 +++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/pathspec.c b/pathspec.c
index 7a229d8d22..d5b9c0d792 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -1,3 +1,4 @@
+#include <string.h>
 #include "cache.h"
 #include "config.h"
 #include "dir.h"
@@ -588,6 +589,8 @@ void parse_pathspec(struct pathspec *pathspec,
 
 		init_pathspec_item(item + i, flags, prefix, prefixlen, entry);
 
+		check_missing_glob(entry, item[i].magic);
+
 		if (item[i].magic & PATHSPEC_EXCLUDE)
 			nr_exclude++;
 		if (item[i].magic & magic_mask)
@@ -739,3 +742,13 @@ int match_pathspec_attrs(const struct index_state *istate,
 
 	return 1;
 }
+
+void check_missing_glob(const char *pathspec_entry, int flags) {
+	if (flags & (PATHSPEC_GLOB | PATHSPEC_LITERAL)) {
+		return;
+	}
+
+	if (strstr(pathspec_entry, "**")) {
+		warning(_("Pathspec provided contains `**`, but no :(glob) magic.\nIt will not match 0 or more directories!"));
+	}
+}
diff --git a/pathspec.h b/pathspec.h
index 454ce364fa..913518ebd3 100644
--- a/pathspec.h
+++ b/pathspec.h
@@ -157,5 +157,6 @@ char *find_pathspecs_matching_against_index(const struct pathspec *pathspec,
 int match_pathspec_attrs(const struct index_state *istate,
 			 const char *name, int namelen,
 			 const struct pathspec_item *item);
+void check_missing_glob(const char* pathspec_entry, int flags);
 
 #endif /* PATHSPEC_H */
diff --git a/t/t6130-pathspec-noglob.sh b/t/t6130-pathspec-noglob.sh
index ba7902c9cd..af6cd16f76 100755
--- a/t/t6130-pathspec-noglob.sh
+++ b/t/t6130-pathspec-noglob.sh
@@ -157,4 +157,17 @@ test_expect_success '**/ does not work with :(literal) and --glob-pathspecs' '
 	test_must_be_empty actual
 '
 
+cat > expected <<"EOF"
+warning: Pathspec provided contains `**`, but no :(glob) magic.
+EOF
+test_expect_success '** without :(glob) warns of lacking glob magic' '
+	test_might_fail git stash -- "**/bar" 2>warns &&
+	grep -Ff expected warns
+'
+
+test_expect_success '** with :(literal) does not warn of lacking glob magic' '
+	test_might_fail git stash -- ":(literal)**/bar" 2>warns &&
+	! grep -Ff expected warns
+'
+
 test_done
-- 
2.31.0