filter-branch: return to original dir after filtering

The first thing filter-branch does is to create a temporary
directory, either ".git-rewrite" in the current directory
(which may be the working tree or the repository if bare),
or in a directory specified by "-d". We then chdir to
$tempdir/t as our temporary working directory in which to run
tree filters.

After finishing the filter, we then attempt to go back to
the original directory with "cd ../..". This works in the
.git-rewrite case, but if "-d" is used, we end up in a
random directory. The only thing we do after this chdir is
to run git-read-tree, but that means that:

  1. The working directory is not updated to reflect the
     filtered history.

  2. We dump random files into "$tempdir/.." (e.g., if you
     use "-d /tmp/foo", we dump junk into /tmp).

Fix it by recording the full path to the original directory
and returning there explicitly.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-filter-branch.sh

@@ -217,14 +217,15 @@ t)
 	test -d "$tempdir" &&
 		die "$tempdir already exists, please remove it"
 esac
+orig_dir=$(pwd)
 mkdir -p "$tempdir/t" &&
 tempdir="$(cd "$tempdir"; pwd)" &&
 cd "$tempdir/t" &&
 workdir="$(pwd)" ||
 die ""
 
 # Remove tempdir on exit
-trap 'cd ../..; rm -rf "$tempdir"' 0
+trap 'cd "$orig_dir"; rm -rf "$tempdir"' 0
 
 ORIG_GIT_DIR="$GIT_DIR"
 ORIG_GIT_WORK_TREE="$GIT_WORK_TREE"
@@ -489,7 +490,7 @@ if [ "$filter_tag_name" ]; then
 	done
 fi
 
-cd ../..
+cd "$orig_dir"
 rm -rf "$tempdir"
 
 trap - 0

t/t7003-filter-branch.sh

@@ -64,6 +64,20 @@ test_expect_success 'correct GIT_DIR while using -d' '
 	grep drepo "$TRASHDIR/backup-refs"
 '
 
+test_expect_success 'tree-filter works with -d' '
+	git init drepo-tree &&
+	(
+		cd drepo-tree &&
+		test_commit one &&
+		git filter-branch -d "$TRASHDIR/dfoo" \
+			--tree-filter "echo changed >one.t" &&
+		echo changed >expect &&
+		git cat-file blob HEAD:one.t >actual &&
+		test_cmp expect actual &&
+		test_cmp one.t actual
+	)
+'
+
 test_expect_success 'Fail if commit filter fails' '
 	test_must_fail git filter-branch -f --commit-filter "exit 1" HEAD
 '