clone: validate --origin option before use

Providing a bad origin name to `git clone` currently reports an
'invalid refspec' error instead of a more explicit message explaining
that the `--origin` option was malformed.  This behavior dates back to
since 8434c2f (Build in clone, 2008-04-27).  Reintroduce
validation for the provided `--origin` option, but notably _don't_
include a multi-level check (e.g. "foo/bar") that was present in the
original `git-clone.sh`.  `git remote` allows multi-level remote names
since at least 46220ca (remote.c: Fix overtight refspec validation,
2008-03-20), so that appears to be the desired behavior.

Helped-by: Junio C Hamano <[email protected]>
Helped-by: Derrick Stolee <[email protected]>
Helped-by: Jeff King <[email protected]>
Signed-off-by: Sean Barag <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: sjbarag

builtin/clone.c

@@ -1012,6 +1012,9 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (!option_origin)
 		option_origin = "origin";
 
+	if (!valid_remote_name(option_origin))
+		die(_("'%s' is not a valid remote name"), option_origin);
+
 	repo_name = argv[0];
 
 	path = get_repo_path(repo_name, &is_bundle);