builtin/shortlog: don't set up revisions without repo

It is possible to run git-shortlog(1) outside of a repository by passing
it output from git-log(1) via standard input. Obviously, as there is no
repository in that context, it is thus unsupported to pass any revisions
as arguments.

Regardless of that we still end up calling `setup_revisions()`. While
that works alright, it is somewhat strange. Furthermore, this is about
to cause problems when we unset the default object hash.

Refactor the code to only call `setup_revisions()` when we have a
repository. This is safe to do as we already verify that there are no
arguments when running outside of a repository anyway.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/shortlog.c

@@ -435,7 +435,7 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
 		usage_with_options(shortlog_usage, options);
 	}
 
-	if (setup_revisions(argc, argv, &rev, NULL) != 1) {
+	if (!nongit && setup_revisions(argc, argv, &rev, NULL) != 1) {
 		error(_("unrecognized argument: %s"), argv[1]);
 		usage_with_options(shortlog_usage, options);
 	}