strbuf: avoid calling strbuf_grow() twice in strbuf_addbuf()

Implement strbuf_addbuf() as a normal function in order to avoid calling
strbuf_grow() twice, with the second callinside strbud_add() being a
no-op.  This is slightly faster and also reduces the text size a bit.
Signed-off-by: NRene Scharfe <l.s.r@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

strbuf.c

@@ -197,6 +197,13 @@ void strbuf_add(struct strbuf *sb, const void *data, size_t len)
 	strbuf_setlen(sb, sb->len + len);
 }
 
+void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2)
+{
+	strbuf_grow(sb, sb2->len);
+	memcpy(sb->buf + sb->len, sb2->buf, sb2->len);
+	strbuf_setlen(sb, sb->len + sb2->len);
+}
+
 void strbuf_adddup(struct strbuf *sb, size_t pos, size_t len)
 {
 	strbuf_grow(sb, len);

strbuf.h

@@ -263,11 +263,7 @@ static inline void strbuf_addstr(struct strbuf *sb, const char *s)
 /**
  * Copy the contents of another buffer at the end of the current one.
  */
-static inline void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2)
-{
-	strbuf_grow(sb, sb2->len);
-	strbuf_add(sb, sb2->buf, sb2->len);
-}
+extern void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2);
 
 /**
  * Copy part of the buffer from a given position till a given length to the