Replace all read_fd use with strbuf_read, and get rid of it.

  This brings builtin-stripspace, builtin-tag and mktag to use strbufs.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/mktag.c b/mktag.c
index 38acd5a..7567f9e 100644
--- a/mktag.c
+++ b/mktag.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "strbuf.h"
 #include "tag.h"
 
 /*
@@ -111,8 +112,7 @@
 
 int main(int argc, char **argv)
 {
-	unsigned long size = 4096;
-	char *buffer = xmalloc(size);
+	struct strbuf buf;
 	unsigned char result_sha1[20];
 
 	if (argc != 1)
@@ -120,21 +120,20 @@
 
 	setup_git_directory();
 
-	if (read_fd(0, &buffer, &size)) {
-		free(buffer);
+	strbuf_init(&buf, 0);
+	if (strbuf_read(&buf, 0, 4096) < 0) {
 		die("could not read from stdin");
 	}
 
 	/* Verify it for some basic sanity: it needs to start with
 	   "object <sha1>\ntype\ntagger " */
-	if (verify_tag(buffer, size) < 0)
+	if (verify_tag(buf.buf, buf.len) < 0)
 		die("invalid tag signature file");
 
-	if (write_sha1_file(buffer, size, tag_type, result_sha1) < 0)
+	if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
 		die("unable to write tag file");
 
-	free(buffer);
-
+	strbuf_release(&buf);
 	printf("%s\n", sha1_to_hex(result_sha1));
 	return 0;
 }