Delay "empty ident" errors until they really matter.

Previous one warned people upfront to encourage fixing their
environment early, but some people just use repositories and git
tools read-only without making any changes, and in such a case
there is not much point insisting on them having a usable ident.

This round attempts to move the error until either "git-var"
asks for the ident explicitly or "commit-tree" wants to use it.

Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/commit-tree.c b/commit-tree.c
index b1c8dca..88871b0 100644
--- a/commit-tree.c
+++ b/commit-tree.c
@@ -118,8 +118,8 @@
 		add_buffer(&buffer, &size, "parent %s\n", sha1_to_hex(parent_sha1[i]));
 
 	/* Person/date information */
-	add_buffer(&buffer, &size, "author %s\n", git_author_info());
-	add_buffer(&buffer, &size, "committer %s\n\n", git_committer_info());
+	add_buffer(&buffer, &size, "author %s\n", git_author_info(1));
+	add_buffer(&buffer, &size, "committer %s\n\n", git_committer_info(1));
 
 	/* And add the comment */
 	while (fgets(comment, sizeof(comment), stdin) != NULL)