Separate object name errors from usage errors

Separate object name errors from usage errors.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/revision.c b/revision.c
index 5f2f0be..d41e59b 100644
--- a/revision.c
+++ b/revision.c
@@ -674,7 +674,7 @@
 			local_flags = UNINTERESTING;
 			arg++;
 		}
-		if (get_sha1(arg, sha1) < 0) {
+		if (get_sha1(arg, sha1)) {
 			int j;
 
 			if (seen_dashdash || local_flags)
@@ -693,7 +693,7 @@
 	if (def && !revs->commits) {
 		unsigned char sha1[20];
 		struct commit *commit;
-		if (get_sha1(def, sha1) < 0)
+		if (get_sha1(def, sha1))
 			die("bad default revision '%s'", def);
 		commit = get_commit_reference(revs, def, sha1, 0);
 		add_one_commit(commit, revs);