scalar: add a test toggle to skip accessing the vsts/info endpoint

In Scalar's functional tests, we do not do anything with authentication.
Therefore, we do want to avoid accessing the `vsts/info` endpoint
because it requires authentication even on otherwise public
repositories.

Let's introduce the environment variable `SCALAR_TEST_SKIP_VSTS_INFO`
which can be set to `true` to simply skip that step (and force the
`url_*` style repository IDs instead of `id_*` whenever possible).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

scalar.c

@@ -516,7 +516,8 @@ static char *get_cache_key(const char *url)
 	 * The GVFS protocol is only supported via https://; For testing, we
 	 * also allow http://.
 	 */
-	if (can_url_support_gvfs(url)) {
+	if (!git_env_bool("SCALAR_TEST_SKIP_VSTS_INFO", 0) &&
+	    can_url_support_gvfs(url)) {
 		cp.git_cmd = 1;
 		strvec_pushl(&cp.args, "gvfs-helper", "--remote", url,
 			     "endpoint", "vsts/info", NULL);