strbuf: use strbuf_addstr() for adding C strings

Avoid code duplication and let strbuf_addstr() call strlen() for us.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/diff.c b/diff.c
index 06bdfb8..867f034 100644
--- a/diff.c
+++ b/diff.c
@@ -525,9 +525,9 @@
 	ep += 2; /* skip over @@ */
 
 	/* The hunk header in fraginfo color */
-	strbuf_add(&msgbuf, frag, strlen(frag));
+	strbuf_addstr(&msgbuf, frag);
 	strbuf_add(&msgbuf, line, ep - line);
-	strbuf_add(&msgbuf, reset, strlen(reset));
+	strbuf_addstr(&msgbuf, reset);
 
 	/*
 	 * trailing "\r\n"
@@ -541,15 +541,15 @@
 		if (*ep != ' ' && *ep != '\t')
 			break;
 	if (ep != cp) {
-		strbuf_add(&msgbuf, plain, strlen(plain));
+		strbuf_addstr(&msgbuf, plain);
 		strbuf_add(&msgbuf, cp, ep - cp);
-		strbuf_add(&msgbuf, reset, strlen(reset));
+		strbuf_addstr(&msgbuf, reset);
 	}
 
 	if (ep < line + len) {
-		strbuf_add(&msgbuf, func, strlen(func));
+		strbuf_addstr(&msgbuf, func);
 		strbuf_add(&msgbuf, ep, line + len - ep);
-		strbuf_add(&msgbuf, reset, strlen(reset));
+		strbuf_addstr(&msgbuf, reset);
 	}
 
 	strbuf_add(&msgbuf, line + len, org_len - len);