-# $head is the token given from the command line. If a ref with that
-# name exists at the remote and their values match, we should use it.
-# Otherwise find a ref that matches $headrev.
+# $head is the token given from the command line, and $tag_name, if
+# exists, is the tag we are going to show the commit information for.
+# If that tag exists at the remote and it points at the commit, use it.
+# Otherwise, if a branch with the same name as $head exists at the remote
+# and their values match, use that instead.
+#
+# Otherwise find a random ref that matches $headrev.