use strbuf_addch for adding single characters

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -171,7 +171,7 @@ static void output(struct merge_options *o, int v, const char *fmt, ...)
 	strbuf_vaddf(&o->obuf, fmt, ap);
 	va_end(ap);
 
-	strbuf_add(&o->obuf, "\n", 1);
+	strbuf_addch(&o->obuf, '\n');
 	if (!o->buffer_output)
 		flush_output(o);
 }

pathspec.c

@@ -338,7 +338,7 @@ static void NORETURN unsupported_magic(const char *pattern,
 		if (!(magic & m->bit))
 			continue;
 		if (sb.len)
-			strbuf_addstr(&sb, " ");
+			strbuf_addch(&sb, ' ');
 		if (short_magic & m->bit)
 			strbuf_addf(&sb, "'%c'", m->mnemonic);
 		else

url.c

@@ -121,7 +121,7 @@ void end_url_with_slash(struct strbuf *buf, const char *url)
 {
 	strbuf_addstr(buf, url);
 	if (buf->len && buf->buf[buf->len - 1] != '/')
-		strbuf_addstr(buf, "/");
+		strbuf_addch(buf, '/');
 }
 
 void str_end_url_with_slash(const char *url, char **dest) {