git-fsck: add --lost-found option

With this option, dangling objects are not only reported, but also
written to .git/lost-found/commit/ or .git/lost-found/other/. This
option implies '--full' and '--no-reflogs'.

'git fsck --lost-found' is meant as a replacement for git-lost-found.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-fsck.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git-fsck' [--tags] [--root] [--unreachable] [--cache] [--no-reflogs]
-		 [--full] [--strict] [--verbose] [<object>*]
+	 [--full] [--strict] [--verbose] [--lost-found] [<object>*]
 
 DESCRIPTION
 -----------
@@ -64,6 +64,10 @@ index file and all SHA1 references in .git/refs/* as heads.
 --verbose::
 	Be chatty.
 
+--lost-found::
+	Write dangling refs into .git/commit/ or .git/other/, depending
+	on type.
+
 It tests SHA1 and general object sanity, and it does full tracking of
 the resulting reachability and everything else. It prints out any
 corruption it finds (missing or bad objects), and if you use the

builtin-fsck.c

@@ -20,6 +20,7 @@ static int check_strict;
 static int keep_cache_objects;
 static unsigned char head_sha1[20];
 static int errors_found;
+static int write_lost_and_found;
 static int verbose;
 #define ERROR_OBJECT 01
 #define ERROR_REACHABLE 02
@@ -138,6 +139,21 @@ static void check_unreachable_object(struct object *obj)
 	if (!obj->used) {
 		printf("dangling %s %s\n", typename(obj->type),
 		       sha1_to_hex(obj->sha1));
+		if (write_lost_and_found) {
+			char *filename = git_path("lost-found/%s/%s",
+				obj->type == OBJ_COMMIT ? "commit" : "other",
+				sha1_to_hex(obj->sha1));
+			FILE *f;
+
+			if (safe_create_leading_directories(filename)) {
+				error("Could not create lost-found");
+				return;
+			}
+			if (!(f = fopen(filename, "w")))
+				die("Could not open %s", filename);
+			fprintf(f, "%s\n", sha1_to_hex(obj->sha1));
+			fclose(f);
+		}
 		return;
 	}
 
@@ -685,6 +701,12 @@ int cmd_fsck(int argc, char **argv, const char *prefix)
 			verbose = 1;
 			continue;
 		}
+		if (!strcmp(arg, "--lost-found")) {
+			check_full = 1;
+			include_reflogs = 0;
+			write_lost_and_found = 1;
+			continue;
+		}
 		if (*arg == '-')
 			usage(fsck_usage);
 	}

t/t1420-lost-found.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+#
+# Copyright (c) 2007 Johannes E. Schindelin
+#
+
+test_description='Test fsck --lost-found'
+. ./test-lib.sh
+
+test_expect_success setup '
+	git config core.logAllRefUpdates 0 &&
+	: > file1 &&
+	git add file1 &&
+	test_tick &&
+	git commit -m initial &&
+	echo 1 > file1 &&
+	echo 2 > file2 &&
+	git add file1 file2 &&
+	test_tick &&
+	git commit -m second &&
+	echo 3 > file3 &&
+	git add file3
+'
+
+test_expect_success 'lost and found something' '
+	git rev-parse HEAD > lost-commit &&
+	git rev-parse :file3 > lost-other &&
+	test_tick &&
+	git reset --hard HEAD^ &&
+	git fsck --lost-found &&
+	test 2 = $(ls .git/lost-found/*/* | wc -l) &&
+	test -f .git/lost-found/commit/$(cat lost-commit) &&
+	test -f .git/lost-found/other/$(cat lost-other)
+'
+
+test_done