2 files changed, 31 insertions, 0 deletions
diff --git a/builtin/remote.c b/builtin/remote.c
index 0d6755bcb7..a770df669c 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -157,6 +157,21 @@ static int parse_mirror_opt(const struct option *opt, const char *arg, int not)
 	return 0;
 }
 
+static int check_remote_collision(struct remote *remote, void *data)
+{
+	const char *name = data;
+	const char *p;
+
+	if (skip_prefix(name, remote->name, &p) && *p == '/')
+		die(_("remote name '%s' is a subset of existing remote '%s'"),
+		    name, remote->name);
+	if (skip_prefix(remote->name, name, &p) && *p == '/')
+		die(_("remote name '%s' is a superset of existing remote '%s'"),
+		    name, remote->name);
+
+	return 0;
+}
+
 static int add(int argc, const char **argv, const char *prefix,
 	       struct repository *repo UNUSED)
 {
@@ -208,6 +223,8 @@ static int add(int argc, const char **argv, const char *prefix,
 	if (!valid_remote_name(name))
 		die(_("'%s' is not a valid remote name"), name);
 
+	for_each_remote(check_remote_collision, (void *)name);
+
 	strbuf_addf(&buf, "remote.%s.url", name);
 	git_config_set(buf.buf, url);
 
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index bef0250e89..2701eef85e 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -1644,4 +1644,18 @@ test_expect_success 'empty config clears remote.*.pushurl list' '
 	test_cmp expect actual
 '
 
+test_expect_success 'forbid adding subset of existing remote' '
+	test_when_finished "git remote rm outer" &&
+	git remote add outer url &&
+	test_must_fail git remote add outer/inner url 2>err &&
+	test_grep ".outer/inner. is a subset of existing remote .outer." err
+'
+
+test_expect_success 'forbid adding superset of existing remote' '
+	test_when_finished "git remote rm outer/inner" &&
+	git remote add outer/inner url &&
+	test_must_fail git remote add outer url 2>err &&
+	test_grep ".outer. is a superset of existing remote .outer/inner." err
+'
+
 test_done