Handle missing timestamp in commit/tag objects

When a commit or tag lacks author/committer/tagger timestamp, do not skip
the next line in the commit/tag object.

Also, do not bother to print timestamps with value 0 as it is close to certain
to be bogus.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

parsing.c

@@ -218,7 +218,7 @@ struct commitinfo *cgit_parse_commit(struct commit *commit)
 		p = t;
 		t = strchr(t, '>') + 1;
 		ret->author_email = substr(p, t);
-		ret->author_date = atol(++t);
+		ret->author_date = atol(t+1);
 		p = strchr(t, '\n') + 1;
 	}
 
@@ -229,7 +229,7 @@ struct commitinfo *cgit_parse_commit(struct commit *commit)
 		p = t;
 		t = strchr(t, '>') + 1;
 		ret->committer_email = substr(p, t);
-		ret->committer_date = atol(++t);
+		ret->committer_date = atol(t+1);
 		p = strchr(t, '\n') + 1;
 	}
 
@@ -290,7 +290,7 @@ struct taginfo *cgit_parse_tag(struct tag *tag)
 			p = t;
 			t = strchr(t, '>') + 1;
 			ret->tagger_email = substr(p, t);
-			ret->tagger_date = atol(++t);
+			ret->tagger_date = atol(t+1);
 		}
 		p = strchr(p, '\n') + 1;
 	}