buf: add consume_bytes

Allow users to consume a buffer by the number of bytes, not just to an
ending pointer.

src/buffer.c

@@ -567,6 +567,11 @@ void git_buf_copy_cstr(char *data, size_t datasize, const git_buf *buf)
 	data[copylen] = '\0';
 }
 
+void git_buf_consume_bytes(git_buf *buf, size_t len)
+{
+	git_buf_consume(buf, buf->ptr + len);
+}
+
 void git_buf_consume(git_buf *buf, const char *end)
 {
 	if (end > buf->ptr && end <= buf->ptr + buf->size) {

src/buffer.h

@@ -113,6 +113,7 @@ int git_buf_puts(git_buf *buf, const char *string);
 int git_buf_printf(git_buf *buf, const char *format, ...) GIT_FORMAT_PRINTF(2, 3);
 int git_buf_vprintf(git_buf *buf, const char *format, va_list ap);
 void git_buf_clear(git_buf *buf);
+void git_buf_consume_bytes(git_buf *buf, size_t len);
 void git_buf_consume(git_buf *buf, const char *end);
 void git_buf_truncate(git_buf *buf, size_t len);
 void git_buf_shorten(git_buf *buf, size_t amount);