fsck: HEAD is part of refs

By default we looked at all refs but not HEAD.  The only thing that made
fsck not lose sight of commits that are only reachable from a detached
HEAD was the reflog for the HEAD.

This fixes it, with a new test.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-fsck.c

@@ -23,6 +23,7 @@ static int check_full;
 static int check_strict;
 static int keep_cache_objects;
 static unsigned char head_sha1[20];
+static const char *head_points_at;
 static int errors_found;
 static int write_lost_and_found;
 static int verbose;
@@ -473,6 +474,8 @@ static int fsck_handle_ref(const char *refname, const unsigned char *sha1, int f
 
 static void get_default_heads(void)
 {
+	if (head_points_at && !is_null_sha1(head_sha1))
+		fsck_handle_ref("HEAD", head_sha1, 0, NULL);
 	for_each_ref(fsck_handle_ref, NULL);
 	if (include_reflogs)
 		for_each_reflog(fsck_handle_reflog, NULL);
@@ -512,14 +515,13 @@ static void fsck_object_dir(const char *path)
 
 static int fsck_head_link(void)
 {
-	unsigned char sha1[20];
 	int flag;
 	int null_is_error = 0;
-	const char *head_points_at = resolve_ref("HEAD", sha1, 0, &flag);
 
 	if (verbose)
 		fprintf(stderr, "Checking HEAD link\n");
 
+	head_points_at = resolve_ref("HEAD", head_sha1, 0, &flag);
 	if (!head_points_at)
 		return error("Invalid HEAD");
 	if (!strcmp(head_points_at, "HEAD"))
@@ -528,7 +530,7 @@ static int fsck_head_link(void)
 	else if (prefixcmp(head_points_at, "refs/heads/"))
 		return error("HEAD points to something strange (%s)",
 			     head_points_at);
-	if (is_null_sha1(sha1)) {
+	if (is_null_sha1(head_sha1)) {
 		if (null_is_error)
 			return error("HEAD: detached HEAD points at nothing");
 		fprintf(stderr, "notice: HEAD points to an unborn branch (%s)\n",
@@ -624,8 +626,9 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
 	heads = 0;
 	for (i = 0; i < argc; i++) {
 		const char *arg = argv[i];
-		if (!get_sha1(arg, head_sha1)) {
-			struct object *obj = lookup_object(head_sha1);
+		unsigned char sha1[20];
+		if (!get_sha1(arg, sha1)) {
+			struct object *obj = lookup_object(sha1);
 
 			/* Error is printed by lookup_object(). */
 			if (!obj)

t/t1450-fsck.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+test_description='git fsck random collection of tests'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_commit A fileA one &&
+	git checkout HEAD^0 &&
+	test_commit B fileB two &&
+	git tag -d A B &&
+	git reflog expire --expire=now --all
+'
+
+test_expect_success 'HEAD is part of refs' '
+	test 0 = $(git fsck | wc -l)
+'
+
+test_done