submodule: ignore trailing slash in relative url

This is similar to the previous patch, though no user reported a bug and
I could not find a regressive behavior.

However it is a good thing to be strict on the output and for that we
always omit a trailing slash.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/submodule--helper.c

@@ -149,6 +149,8 @@ static char *relative_url(const char *remote_url,
 	}
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s%s%s", remoteurl, colonsep ? ":" : "/", url);
+	if (ends_with(url, "/"))
+		strbuf_setlen(&sb, sb.len - 1);
 	free(remoteurl);
 
 	if (starts_with_dot_slash(sb.buf))

t/t0060-path-utils.sh

@@ -319,6 +319,7 @@ test_submodule_relative_url "../" "foo/bar" "../submodule" "../foo/submodule"
 test_submodule_relative_url "../" "foo" "../submodule" "../submodule"
 
 test_submodule_relative_url "(null)" "../foo/bar" "../sub/a/b/c" "../foo/sub/a/b/c"
+test_submodule_relative_url "(null)" "../foo/bar" "../sub/a/b/c/" "../foo/sub/a/b/c"
 test_submodule_relative_url "(null)" "../foo/bar/" "../sub/a/b/c" "../foo/sub/a/b/c"
 test_submodule_relative_url "(null)" "../foo/bar" "../submodule" "../foo/submodule"
 test_submodule_relative_url "(null)" "../foo/submodule" "../submodule" "../foo/submodule"