Merge branch 'js/shallow-and-fetch-prune'

"git repack" in a shallow clone did not correctly update the
shallow points in the repository, leading to a repository that
does not pass fsck.

* js/shallow-and-fetch-prune:
  repack -ad: prune the list of shallow commits
  shallow: offer to prune only non-existing entries
  repack: point out a bug handling stale shallow info

builtin/repack.c

@@ -550,6 +550,12 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 		if (!po_args.quiet && isatty(2))
 			opts |= PRUNE_PACKED_VERBOSE;
 		prune_packed_objects(opts);
+
+		if (!keep_unreachable &&
+		    (!(pack_everything & LOOSEN_UNREACHABLE) ||
+		     unpack_unreachable) &&
+		    is_repository_shallow(the_repository))
+			prune_shallow(PRUNE_QUICK);
 	}
 
 	if (!no_update_server_info)