Make some strbuf_*() struct strbuf arguments const.

Signed-off-by: Lukas Sandström <lukass@etek.chalmers.se>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

strbuf.c

@@ -67,7 +67,7 @@ void strbuf_rtrim(struct strbuf *sb)
 	sb->buf[sb->len] = '\0';
 }
 
-int strbuf_cmp(struct strbuf *a, struct strbuf *b)
+int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
 {
 	int cmp;
 	if (a->len < b->len) {

strbuf.h

@@ -61,7 +61,7 @@ static inline void strbuf_swap(struct strbuf *a, struct strbuf *b) {
 }
 
 /*----- strbuf size related -----*/
-static inline size_t strbuf_avail(struct strbuf *sb) {
+static inline size_t strbuf_avail(const struct strbuf *sb) {
 	return sb->alloc ? sb->alloc - sb->len - 1 : 0;
 }
 
@@ -78,7 +78,7 @@ static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
 
 /*----- content related -----*/
 extern void strbuf_rtrim(struct strbuf *);
-extern int strbuf_cmp(struct strbuf *, struct strbuf *);
+extern int strbuf_cmp(const struct strbuf *, const struct strbuf *);
 
 /*----- add data in your buffer -----*/
 static inline void strbuf_addch(struct strbuf *sb, int c) {
@@ -98,7 +98,7 @@ extern void strbuf_add(struct strbuf *, const void *, size_t);
 static inline void strbuf_addstr(struct strbuf *sb, const char *s) {
 	strbuf_add(sb, s, strlen(s));
 }
-static inline void strbuf_addbuf(struct strbuf *sb, struct strbuf *sb2) {
+static inline void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2) {
 	strbuf_add(sb, sb2->buf, sb2->len);
 }
 extern void strbuf_adddup(struct strbuf *sb, size_t pos, size_t len);