Merge branch 'es/mark-gc-cruft-as-experimental'

Enable gc.cruftpacks by default for those who opt into
feature.experimental setting.

* es/mark-gc-cruft-as-experimental:
  config: let feature.experimental imply gc.cruftPacks=true
  gc: add tests for --cruft and friends

repo-settings.c

@@ -43,6 +43,7 @@ void prepare_repo_settings(struct repository *r)
 	/* Defaults modified by feature.* */
 	if (experimental) {
 		r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_SKIPPING;
+		r->settings.gc_cruft_packs = 1;
 	}
 	if (manyfiles) {
 		r->settings.index_version = 4;