git-filter-branch.sh - jrn/git - Git at Google

 #!/bin/sh
 #
 # Rewrite revision history
 # Copyright (c) Petr Baudis, 2006
 # Minimal changes to "port" it to core-git (c) Johannes Schindelin, 2007
 #
 # Lets you rewrite the revision history of the current branch, creating
 # a new branch. You can specify a number of filters to modify the commits,
 # files and trees.

 # The following functions will also be available in the commit filter:

 functions=$(cat << \EOF
 warn () {
 	echo "$*" >&2
 }

 map()
 {
 	# if it was not rewritten, take the original
 	if test -r "$workdir/../map/$1"
 	then
 		cat "$workdir/../map/$1"
 	else
 		echo "$1"
 	fi
 }

 # if you run 'skip_commit "$@"' in a commit filter, it will print
 # the (mapped) parents, effectively skipping the commit.

 skip_commit()
 {
 	shift;
 	while [ -n "$1" ];
 	do
 		shift;
 		map "$1";
 		shift;
 	done;
 }

 # if you run 'git_commit_non_empty_tree "$@"' in a commit filter,
 # it will skip commits that leave the tree untouched, commit the other.
 git_commit_non_empty_tree()
 {
 	if test $# = 3 && test "$1" = $(git rev-parse "$3^{tree}"); then
 		map "$3"
 	elif test $# = 1 && test "$1" = 4b825dc642cb6eb9a060e54bf8d69288fbee4904; then
 		:
 	else
 		git commit-tree "$@"
 	fi
 }
 # override die(): this version puts in an extra line break, so that
 # the progress is still visible

 die()
 {
 	echo >&2
 	echo "$*" >&2
 	exit 1
 }
 EOF
 )

 eval "$functions"

 finish_ident() {
 	# Ensure non-empty id name.
 	echo "case \"\$GIT_$1_NAME\" in \"\") GIT_$1_NAME=\"\${GIT_$1_EMAIL%%@*}\" && export GIT_$1_NAME;; esac"
 	# And make sure everything is exported.
 	echo "export GIT_$1_NAME"
 	echo "export GIT_$1_EMAIL"
 	echo "export GIT_$1_DATE"
 }

 set_ident () {
 	parse_ident_from_commit author AUTHOR committer COMMITTER
 	finish_ident AUTHOR
 	finish_ident COMMITTER
 }

 USAGE="[--setup <command>] [--subdirectory-filter <directory>] [--env-filter <command>]
 	[--tree-filter <command>] [--index-filter <command>]
 	[--parent-filter <command>] [--msg-filter <command>]
 	[--commit-filter <command>] [--tag-name-filter <command>]
 	[--original <namespace>]
 	[-d <directory>] [-f | --force] [--state-branch <branch>]
 	[--] [<rev-list options>...]"

 OPTIONS_SPEC=
 . git-sh-setup

 if [ "$(is_bare_repository)" = false ]; then
 	require_clean_work_tree 'rewrite branches'
 fi

 tempdir=.git-rewrite
 filter_setup=
 filter_env=
 filter_tree=
 filter_index=
 filter_parent=
 filter_msg=cat
 filter_commit=
 filter_tag_name=
 filter_subdir=
 state_branch=
 orig_namespace=refs/original/
 force=
 prune_empty=
 remap_to_ancestor=
 while :
 do
 	case "$1" in
 	--)
 		shift
 		break
 		;;
 	--force|-f)
 		shift
 		force=t
 		continue
 		;;
 	--remap-to-ancestor)
 		# deprecated ($remap_to_ancestor is set now automatically)
 		shift
 		remap_to_ancestor=t
 		continue
 		;;
 	--prune-empty)
 		shift
 		prune_empty=t
 		continue
 		;;
 	-*)
 		;;
 	*)
 		break;
 	esac

 	# all switches take one argument
 	ARG="$1"
 	case "$#" in 1) usage ;; esac
 	shift
 	OPTARG="$1"
 	shift

 	case "$ARG" in
 	-d)
 		tempdir="$OPTARG"
 		;;
 	--setup)
 		filter_setup="$OPTARG"
 		;;
 	--subdirectory-filter)
 		filter_subdir="$OPTARG"
 		remap_to_ancestor=t
 		;;
 	--env-filter)
 		filter_env="$OPTARG"
 		;;
 	--tree-filter)
 		filter_tree="$OPTARG"
 		;;
 	--index-filter)
 		filter_index="$OPTARG"
 		;;
 	--parent-filter)
 		filter_parent="$OPTARG"
 		;;
 	--msg-filter)
 		filter_msg="$OPTARG"
 		;;
 	--commit-filter)
 		filter_commit="$functions; $OPTARG"
 		;;
 	--tag-name-filter)
 		filter_tag_name="$OPTARG"
 		;;
 	--original)
 		orig_namespace=$(expr "$OPTARG/" : '\(.*[^/]\)/*$')/
 		;;
 	--state-branch)
 		state_branch="$OPTARG"
 		;;
 	*)
 		usage
 		;;
 	esac
 done

 case "$prune_empty,$filter_commit" in
 ,)
 	filter_commit='git commit-tree "$@"';;
 t,)
 	filter_commit="$functions;"' git_commit_non_empty_tree "$@"';;
 ,*)
 	;;
 *)
 	die "Cannot set --prune-empty and --commit-filter at the same time"
 esac

 case "$force" in
 t)
 	rm -rf "$tempdir"
 ;;
 '')
 	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 "$orig_dir"; rm -rf "$tempdir"' 0

 ORIG_GIT_DIR="$GIT_DIR"
 ORIG_GIT_WORK_TREE="$GIT_WORK_TREE"
 ORIG_GIT_INDEX_FILE="$GIT_INDEX_FILE"
 ORIG_GIT_AUTHOR_NAME="$GIT_AUTHOR_NAME"
 ORIG_GIT_AUTHOR_EMAIL="$GIT_AUTHOR_EMAIL"
 ORIG_GIT_AUTHOR_DATE="$GIT_AUTHOR_DATE"
 ORIG_GIT_COMMITTER_NAME="$GIT_COMMITTER_NAME"
 ORIG_GIT_COMMITTER_EMAIL="$GIT_COMMITTER_EMAIL"
 ORIG_GIT_COMMITTER_DATE="$GIT_COMMITTER_DATE"

 GIT_WORK_TREE=.
 export GIT_DIR GIT_WORK_TREE

 # Make sure refs/original is empty
 git for-each-ref > "$tempdir"/backup-refs || exit
 while read sha1 type name
 do
 	case "$force,$name" in
 	,$orig_namespace*)
 		die "Cannot create a new backup.
 A previous backup already exists in $orig_namespace
 Force overwriting the backup with -f"
 	;;
 	t,$orig_namespace*)
 		git update-ref -d "$name" $sha1
 	;;
 	esac
 done < "$tempdir"/backup-refs

 # The refs should be updated if their heads were rewritten
 git rev-parse --no-flags --revs-only --symbolic-full-name \
 	--default HEAD "$@" > "$tempdir"/raw-heads || exit
 sed -e '/^^/d' "$tempdir"/raw-heads >"$tempdir"/heads

 test -s "$tempdir"/heads ||
 	die "You must specify a ref to rewrite."

 GIT_INDEX_FILE="$(pwd)/../index"
 export GIT_INDEX_FILE

 # map old->new commit ids for rewriting parents
 mkdir ../map || die "Could not create map/ directory"

 if test -n "$state_branch"
 then
 	state_commit=$(git rev-parse --no-flags --revs-only "$state_branch")
 	if test -n "$state_commit"
 	then
 		echo "Populating map from $state_branch ($state_commit)" 1>&2
 		perl -e'open(MAP, "-|", "git show $ARGV[0]:filter.map") or die;
 			while (<MAP>) {
 				m/(.*):(.*)/ or die;
 				open F, ">../map/$1" or die;
 				print F "$2" or die;
 				close(F) or die;
 			}
 			close(MAP) or die;' "$state_commit" \
 				|| die "Unable to load state from $state_branch:filter.map"
 	else
 		echo "Branch $state_branch does not exist. Will create" 1>&2
 	fi
 fi

 # we need "--" only if there are no path arguments in $@
 nonrevs=$(git rev-parse --no-revs "$@") || exit
 if test -z "$nonrevs"
 then
 	dashdash=--
 else
 	dashdash=
 	remap_to_ancestor=t
 fi

 git rev-parse --revs-only "$@" >../parse

 case "$filter_subdir" in
 "")
 	eval set -- "$(git rev-parse --sq --no-revs "$@")"
 	;;
 *)
 	eval set -- "$(git rev-parse --sq --no-revs "$@" $dashdash \
 		"$filter_subdir")"
 	;;
 esac

 git rev-list --reverse --topo-order --default HEAD \
 	--parents --simplify-merges --stdin "$@" <../parse >../revs ||
 	die "Could not get the commits"
 commits=$(wc -l <../revs | tr -d " ")

 test $commits -eq 0 && die "Found nothing to rewrite"

 # Rewrite the commits
 report_progress ()
 {
 	if test -n "$progress" &&
 		test $git_filter_branch__commit_count -gt $next_sample_at
 	then
 		count=$git_filter_branch__commit_count

 		now=$(date +%s)
 		elapsed=$(($now - $start_timestamp))
 		remaining=$(( ($commits - $count) * $elapsed / $count ))
 		if test $elapsed -gt 0
 		then
 			next_sample_at=$(( ($elapsed + 1) * $count / $elapsed ))
 		else
 			next_sample_at=$(($next_sample_at + 1))
 		fi
 		progress=" ($elapsed seconds passed, remaining $remaining predicted)"
 	fi
 	printf "\rRewrite $commit ($count/$commits)$progress    "
 }

 git_filter_branch__commit_count=0

 progress= start_timestamp=
 if date '+%s' 2>/dev/null | grep -q '^[0-9][0-9]*$'
 then
 	next_sample_at=0
 	progress="dummy to ensure this is not empty"
 	start_timestamp=$(date '+%s')
 fi

 if test -n "$filter_index" ||
    test -n "$filter_tree" ||
    test -n "$filter_subdir"
 then
 	need_index=t
 else
 	need_index=
 fi

 eval "$filter_setup" < /dev/null ||
 	die "filter setup failed: $filter_setup"

 while read commit parents; do
 	git_filter_branch__commit_count=$(($git_filter_branch__commit_count+1))

 	report_progress

 	case "$filter_subdir" in
 	"")
 		if test -n "$need_index"
 		then
 			GIT_ALLOW_NULL_SHA1=1 git read-tree -i -m $commit
 		fi
 		;;
 	*)
 		# The commit may not have the subdirectory at all
 		err=$(GIT_ALLOW_NULL_SHA1=1 \
 		      git read-tree -i -m $commit:"$filter_subdir" 2>&1) || {
 			if ! git rev-parse -q --verify $commit:"$filter_subdir"
 			then
 				rm -f "$GIT_INDEX_FILE"
 			else
 				echo >&2 "$err"
 				false
 			fi
 		}
 	esac || die "Could not initialize the index"

 	GIT_COMMIT=$commit
 	export GIT_COMMIT
 	git cat-file commit "$commit" >../commit ||
 		die "Cannot read commit $commit"

 	eval "$(set_ident <../commit)" ||
 		die "setting author/committer failed for commit $commit"
 	eval "$filter_env" < /dev/null ||
 		die "env filter failed: $filter_env"

 	if [ "$filter_tree" ]; then
 		git checkout-index -f -u -a ||
 			die "Could not checkout the index"
 		# files that $commit removed are now still in the working tree;
 		# remove them, else they would be added again
 		git clean -d -q -f -x
 		eval "$filter_tree" < /dev/null ||
 			die "tree filter failed: $filter_tree"

 		(
 			git diff-index -r --name-only --ignore-submodules $commit -- &&
 			git ls-files --others
 		) > "$tempdir"/tree-state || exit
 		git update-index --add --replace --remove --stdin \
 			< "$tempdir"/tree-state || exit
 	fi

 	eval "$filter_index" < /dev/null ||
 		die "index filter failed: $filter_index"

 	parentstr=
 	for parent in $parents; do
 		for reparent in $(map "$parent"); do
 			case "$parentstr " in
 			*" -p $reparent "*)
 				;;
 			*)
 				parentstr="$parentstr -p $reparent"
 				;;
 			esac
 		done
 	done
 	if [ "$filter_parent" ]; then
 		parentstr="$(echo "$parentstr" | eval "$filter_parent")" ||
 				die "parent filter failed: $filter_parent"
 	fi

 	{
 		while IFS='' read -r header_line && test -n "$header_line"
 		do
 			# skip header lines...
 			:;
 		done
 		# and output the actual commit message
 		cat
 	} <../commit |
 		eval "$filter_msg" > ../message ||
 			die "msg filter failed: $filter_msg"

 	if test -n "$need_index"
 	then
 		tree=$(git write-tree)
 	else
 		tree=$(git rev-parse "$commit^{tree}")
 	fi
 	workdir=$workdir @SHELL_PATH@ -c "$filter_commit" "git commit-tree" \
 		"$tree" $parentstr < ../message > ../map/$commit ||
 			die "could not write rewritten commit"
 done <../revs

 # If we are filtering for paths, as in the case of a subdirectory
 # filter, it is possible that a specified head is not in the set of
 # rewritten commits, because it was pruned by the revision walker.
 # Ancestor remapping fixes this by mapping these heads to the unique
 # nearest ancestor that survived the pruning.

 if test "$remap_to_ancestor" = t
 then
 	while read ref
 	do
 		sha1=$(git rev-parse "$ref"^0)
 		test -f "$workdir"/../map/$sha1 && continue
 		ancestor=$(git rev-list --simplify-merges -1 "$ref" "$@")
 		test "$ancestor" && echo $(map $ancestor) >> "$workdir"/../map/$sha1
 	done < "$tempdir"/heads
 fi

 # Finally update the refs

 _x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
 _x40="$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40"
 echo
 while read ref
 do
 	# avoid rewriting a ref twice
 	test -f "$orig_namespace$ref" && continue

 	sha1=$(git rev-parse "$ref"^0)
 	rewritten=$(map $sha1)

 	test $sha1 = "$rewritten" &&
 		warn "WARNING: Ref '$ref' is unchanged" &&
 		continue

 	case "$rewritten" in
 	'')
 		echo "Ref '$ref' was deleted"
 		git update-ref -m "filter-branch: delete" -d "$ref" $sha1 ||
 			die "Could not delete $ref"
 	;;
 	$_x40)
 		echo "Ref '$ref' was rewritten"
 		if ! git update-ref -m "filter-branch: rewrite" \
 					"$ref" $rewritten $sha1 2>/dev/null; then
 			if test $(git cat-file -t "$ref") = tag; then
 				if test -z "$filter_tag_name"; then
 					warn "WARNING: You said to rewrite tagged commits, but not the corresponding tag."
 					warn "WARNING: Perhaps use '--tag-name-filter cat' to rewrite the tag."
 				fi
 			else
 				die "Could not rewrite $ref"
 			fi
 		fi
 	;;
 	*)
 		# NEEDSWORK: possibly add -Werror, making this an error
 		warn "WARNING: '$ref' was rewritten into multiple commits:"
 		warn "$rewritten"
 		warn "WARNING: Ref '$ref' points to the first one now."
 		rewritten=$(echo "$rewritten" | head -n 1)
 		git update-ref -m "filter-branch: rewrite to first" \
 				"$ref" $rewritten $sha1 ||
 			die "Could not rewrite $ref"
 	;;
 	esac
 	git update-ref -m "filter-branch: backup" "$orig_namespace$ref" $sha1 ||
 		 exit
 done < "$tempdir"/heads

 # TODO: This should possibly go, with the semantics that all positive given
 #       refs are updated, and their original heads stored in refs/original/
 # Filter tags

 if [ "$filter_tag_name" ]; then
 	git for-each-ref --format='%(objectname) %(objecttype) %(refname)' refs/tags |
 	while read sha1 type ref; do
 		ref="${ref#refs/tags/}"
 		# XXX: Rewrite tagged trees as well?
 		if [ "$type" != "commit" -a "$type" != "tag" ]; then
 			continue;
 		fi

 		if [ "$type" = "tag" ]; then
 			# Dereference to a commit
 			sha1t="$sha1"
 			sha1="$(git rev-parse -q "$sha1"^{commit})" || continue
 		fi

 		[ -f "../map/$sha1" ] || continue
 		new_sha1="$(cat "../map/$sha1")"
 		GIT_COMMIT="$sha1"
 		export GIT_COMMIT
 		new_ref="$(echo "$ref" | eval "$filter_tag_name")" ||
 			die "tag name filter failed: $filter_tag_name"

 		echo "$ref -> $new_ref ($sha1 -> $new_sha1)"

 		if [ "$type" = "tag" ]; then
 			new_sha1=$( ( printf 'object %s\ntype commit\ntag %s\n' \
 						"$new_sha1" "$new_ref"
 				git cat-file tag "$ref" |
 				sed -n \
 				    -e '1,/^$/{
 					  /^object /d
 					  /^type /d
 					  /^tag /d
 					}' \
 				    -e '/^-----BEGIN PGP SIGNATURE-----/q' \
 				    -e 'p' ) |
 				git hash-object -t tag -w --stdin) ||
 				die "Could not create new tag object for $ref"
 			if git cat-file tag "$ref" | \
 			   sane_grep '^-----BEGIN PGP SIGNATURE-----' >/dev/null 2>&1
 			then
 				warn "gpg signature stripped from tag object $sha1t"
 			fi
 		fi

 		git update-ref "refs/tags/$new_ref" "$new_sha1" ||
 			die "Could not write tag $new_ref"
 	done
 fi

 unset GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE
 unset GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL GIT_AUTHOR_DATE
 unset GIT_COMMITTER_NAME GIT_COMMITTER_EMAIL GIT_COMMITTER_DATE
 test -z "$ORIG_GIT_DIR" || {
 	GIT_DIR="$ORIG_GIT_DIR" && export GIT_DIR
 }
 test -z "$ORIG_GIT_WORK_TREE" || {
 	GIT_WORK_TREE="$ORIG_GIT_WORK_TREE" &&
 	export GIT_WORK_TREE
 }
 test -z "$ORIG_GIT_INDEX_FILE" || {
 	GIT_INDEX_FILE="$ORIG_GIT_INDEX_FILE" &&
 	export GIT_INDEX_FILE
 }
 test -z "$ORIG_GIT_AUTHOR_NAME" || {
 	GIT_AUTHOR_NAME="$ORIG_GIT_AUTHOR_NAME" &&
 	export GIT_AUTHOR_NAME
 }
 test -z "$ORIG_GIT_AUTHOR_EMAIL" || {
 	GIT_AUTHOR_EMAIL="$ORIG_GIT_AUTHOR_EMAIL" &&
 	export GIT_AUTHOR_EMAIL
 }
 test -z "$ORIG_GIT_AUTHOR_DATE" || {
 	GIT_AUTHOR_DATE="$ORIG_GIT_AUTHOR_DATE" &&
 	export GIT_AUTHOR_DATE
 }
 test -z "$ORIG_GIT_COMMITTER_NAME" || {
 	GIT_COMMITTER_NAME="$ORIG_GIT_COMMITTER_NAME" &&
 	export GIT_COMMITTER_NAME
 }
 test -z "$ORIG_GIT_COMMITTER_EMAIL" || {
 	GIT_COMMITTER_EMAIL="$ORIG_GIT_COMMITTER_EMAIL" &&
 	export GIT_COMMITTER_EMAIL
 }
 test -z "$ORIG_GIT_COMMITTER_DATE" || {
 	GIT_COMMITTER_DATE="$ORIG_GIT_COMMITTER_DATE" &&
 	export GIT_COMMITTER_DATE
 }

 if test -n "$state_branch"
 then
 	echo "Saving rewrite state to $state_branch" 1>&2
 	state_blob=$(
 		perl -e'opendir D, "../map" or die;
 			open H, "|-", "git hash-object -w --stdin" or die;
 			foreach (sort readdir(D)) {
 				next if m/^\.\.?$/;
 				open F, "<../map/$_" or die;
 				chomp($f = <F>);
 				print H "$_:$f\n" or die;
 			}
 			close(H) or die;' || die "Unable to save state")
 	state_tree=$(/bin/echo -e "100644 blob $state_blob\tfilter.map" | git mktree)
 	if test -n "$state_commit"
 	then
 		state_commit=$(/bin/echo "Sync" | git commit-tree "$state_tree" -p "$state_commit")
 	else
 		state_commit=$(/bin/echo "Sync" | git commit-tree "$state_tree" )
 	fi
 	git update-ref "$state_branch" "$state_commit"
 fi

 cd "$orig_dir"
 rm -rf "$tempdir"

 trap - 0

 if [ "$(is_bare_repository)" = false ]; then
 	git read-tree -u -m HEAD || exit
 fi

 exit 0
	#!/bin/sh
	#
	# Rewrite revision history
	# Copyright (c) Petr Baudis, 2006
	# Minimal changes to "port" it to core-git (c) Johannes Schindelin, 2007
	#
	# Lets you rewrite the revision history of the current branch, creating
	# a new branch. You can specify a number of filters to modify the commits,
	# files and trees.

	# The following functions will also be available in the commit filter:

	functions=$(cat << \EOF
	warn () {
	echo "$*" >&2
	}

	map()
	{
	# if it was not rewritten, take the original
	if test -r "$workdir/../map/$1"
	then
	cat "$workdir/../map/$1"
	else
	echo "$1"
	fi
	}

	# if you run 'skip_commit "$@"' in a commit filter, it will print
	# the (mapped) parents, effectively skipping the commit.

	skip_commit()
	{
	shift;
	while [ -n "$1" ];
	do
	shift;
	map "$1";
	shift;
	done;
	}

	# if you run 'git_commit_non_empty_tree "$@"' in a commit filter,
	# it will skip commits that leave the tree untouched, commit the other.
	git_commit_non_empty_tree()
	{
	if test $# = 3 && test "$1" = $(git rev-parse "$3^{tree}"); then
	map "$3"
	elif test $# = 1 && test "$1" = 4b825dc642cb6eb9a060e54bf8d69288fbee4904; then
	:
	else
	git commit-tree "$@"
	fi
	}
	# override die(): this version puts in an extra line break, so that
	# the progress is still visible

	die()
	{
	echo >&2
	echo "$*" >&2
	exit 1
	}
	EOF
	)

	eval "$functions"

	finish_ident() {
	# Ensure non-empty id name.
	echo "case \"\$GIT_$1_NAME\" in \"\") GIT_$1_NAME=\"\${GIT_$1_EMAIL%%@*}\" && export GIT_$1_NAME;; esac"
	# And make sure everything is exported.
	echo "export GIT_$1_NAME"
	echo "export GIT_$1_EMAIL"
	echo "export GIT_$1_DATE"
	}

	set_ident () {
	parse_ident_from_commit author AUTHOR committer COMMITTER
	finish_ident AUTHOR
	finish_ident COMMITTER
	}

	USAGE="[--setup <command>] [--subdirectory-filter <directory>] [--env-filter <command>]
	[--tree-filter <command>] [--index-filter <command>]
	[--parent-filter <command>] [--msg-filter <command>]
	[--commit-filter <command>] [--tag-name-filter <command>]
	[--original <namespace>]
	[-d <directory>] [-f \| --force] [--state-branch <branch>]
	[--] [<rev-list options>...]"

	OPTIONS_SPEC=
	. git-sh-setup

	if [ "$(is_bare_repository)" = false ]; then
	require_clean_work_tree 'rewrite branches'
	fi

	tempdir=.git-rewrite
	filter_setup=
	filter_env=
	filter_tree=
	filter_index=
	filter_parent=
	filter_msg=cat
	filter_commit=
	filter_tag_name=
	filter_subdir=
	state_branch=
	orig_namespace=refs/original/
	force=
	prune_empty=
	remap_to_ancestor=
	while :
	do
	case "$1" in
	--)
	shift
	break
	;;
	--force\|-f)
	shift
	force=t
	continue
	;;
	--remap-to-ancestor)
	# deprecated ($remap_to_ancestor is set now automatically)
	shift
	remap_to_ancestor=t
	continue
	;;
	--prune-empty)
	shift
	prune_empty=t
	continue
	;;
	-*)
	;;
	*)
	break;
	esac

	# all switches take one argument
	ARG="$1"
	case "$#" in 1) usage ;; esac
	shift
	OPTARG="$1"
	shift

	case "$ARG" in
	-d)
	tempdir="$OPTARG"
	;;
	--setup)
	filter_setup="$OPTARG"
	;;
	--subdirectory-filter)
	filter_subdir="$OPTARG"
	remap_to_ancestor=t
	;;
	--env-filter)
	filter_env="$OPTARG"
	;;
	--tree-filter)
	filter_tree="$OPTARG"
	;;
	--index-filter)
	filter_index="$OPTARG"
	;;
	--parent-filter)
	filter_parent="$OPTARG"
	;;
	--msg-filter)
	filter_msg="$OPTARG"
	;;
	--commit-filter)
	filter_commit="$functions; $OPTARG"
	;;
	--tag-name-filter)
	filter_tag_name="$OPTARG"
	;;
	--original)
	orig_namespace=$(expr "$OPTARG/" : '\(.[^/]\)/$')/
	;;
	--state-branch)
	state_branch="$OPTARG"
	;;
	*)
	usage
	;;
	esac
	done

	case "$prune_empty,$filter_commit" in
	,)
	filter_commit='git commit-tree "$@"';;
	t,)
	filter_commit="$functions;"' git_commit_non_empty_tree "$@"';;
	,*)
	;;
	*)
	die "Cannot set --prune-empty and --commit-filter at the same time"
	esac

	case "$force" in
	t)
	rm -rf "$tempdir"
	;;
	'')
	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 "$orig_dir"; rm -rf "$tempdir"' 0

	ORIG_GIT_DIR="$GIT_DIR"
	ORIG_GIT_WORK_TREE="$GIT_WORK_TREE"
	ORIG_GIT_INDEX_FILE="$GIT_INDEX_FILE"
	ORIG_GIT_AUTHOR_NAME="$GIT_AUTHOR_NAME"
	ORIG_GIT_AUTHOR_EMAIL="$GIT_AUTHOR_EMAIL"
	ORIG_GIT_AUTHOR_DATE="$GIT_AUTHOR_DATE"
	ORIG_GIT_COMMITTER_NAME="$GIT_COMMITTER_NAME"
	ORIG_GIT_COMMITTER_EMAIL="$GIT_COMMITTER_EMAIL"
	ORIG_GIT_COMMITTER_DATE="$GIT_COMMITTER_DATE"

	GIT_WORK_TREE=.
	export GIT_DIR GIT_WORK_TREE

	# Make sure refs/original is empty
	git for-each-ref > "$tempdir"/backup-refs \|\| exit
	while read sha1 type name
	do
	case "$force,$name" in
	,$orig_namespace*)
	die "Cannot create a new backup.
	A previous backup already exists in $orig_namespace
	Force overwriting the backup with -f"
	;;
	t,$orig_namespace*)
	git update-ref -d "$name" $sha1
	;;
	esac
	done < "$tempdir"/backup-refs

	# The refs should be updated if their heads were rewritten
	git rev-parse --no-flags --revs-only --symbolic-full-name \
	--default HEAD "$@" > "$tempdir"/raw-heads \|\| exit
	sed -e '/^^/d' "$tempdir"/raw-heads >"$tempdir"/heads

	test -s "$tempdir"/heads \|\|
	die "You must specify a ref to rewrite."

	GIT_INDEX_FILE="$(pwd)/../index"
	export GIT_INDEX_FILE

	# map old->new commit ids for rewriting parents
	mkdir ../map \|\| die "Could not create map/ directory"

	if test -n "$state_branch"
	then
	state_commit=$(git rev-parse --no-flags --revs-only "$state_branch")
	if test -n "$state_commit"
	then
	echo "Populating map from $state_branch ($state_commit)" 1>&2
	perl -e'open(MAP, "-\|", "git show $ARGV[0]:filter.map") or die;
	while (<MAP>) {
	m/(.):(.)/ or die;
	open F, ">../map/$1" or die;
	print F "$2" or die;
	close(F) or die;
	}
	close(MAP) or die;' "$state_commit" \
	\|\| die "Unable to load state from $state_branch:filter.map"
	else
	echo "Branch $state_branch does not exist. Will create" 1>&2
	fi
	fi

	# we need "--" only if there are no path arguments in $@
	nonrevs=$(git rev-parse --no-revs "$@") \|\| exit
	if test -z "$nonrevs"
	then
	dashdash=--
	else
	dashdash=
	remap_to_ancestor=t
	fi

	git rev-parse --revs-only "$@" >../parse

	case "$filter_subdir" in
	"")
	eval set -- "$(git rev-parse --sq --no-revs "$@")"
	;;
	*)
	eval set -- "$(git rev-parse --sq --no-revs "$@" $dashdash \
	"$filter_subdir")"
	;;
	esac

	git rev-list --reverse --topo-order --default HEAD \
	--parents --simplify-merges --stdin "$@" <../parse >../revs \|\|
	die "Could not get the commits"
	commits=$(wc -l <../revs \| tr -d " ")

	test $commits -eq 0 && die "Found nothing to rewrite"

	# Rewrite the commits
	report_progress ()
	{
	if test -n "$progress" &&
	test $git_filter_branch__commit_count -gt $next_sample_at
	then
	count=$git_filter_branch__commit_count

	now=$(date +%s)
	elapsed=$(($now - $start_timestamp))
	remaining=$(( ($commits - $count) * $elapsed / $count ))
	if test $elapsed -gt 0
	then
	next_sample_at=$(( ($elapsed + 1) * $count / $elapsed ))
	else
	next_sample_at=$(($next_sample_at + 1))
	fi
	progress=" ($elapsed seconds passed, remaining $remaining predicted)"
	fi
	printf "\rRewrite $commit ($count/$commits)$progress "
	}

	git_filter_branch__commit_count=0

	progress= start_timestamp=
	if date '+%s' 2>/dev/null \| grep -q '^[0-9][0-9]*$'
	then
	next_sample_at=0
	progress="dummy to ensure this is not empty"
	start_timestamp=$(date '+%s')
	fi

	if test -n "$filter_index" \|\|
	test -n "$filter_tree" \|\|
	test -n "$filter_subdir"
	then
	need_index=t
	else
	need_index=
	fi

	eval "$filter_setup" < /dev/null \|\|
	die "filter setup failed: $filter_setup"

	while read commit parents; do
	git_filter_branch__commit_count=$(($git_filter_branch__commit_count+1))

	report_progress

	case "$filter_subdir" in
	"")
	if test -n "$need_index"
	then
	GIT_ALLOW_NULL_SHA1=1 git read-tree -i -m $commit
	fi
	;;
	*)
	# The commit may not have the subdirectory at all
	err=$(GIT_ALLOW_NULL_SHA1=1 \
	git read-tree -i -m $commit:"$filter_subdir" 2>&1) \|\| {
	if ! git rev-parse -q --verify $commit:"$filter_subdir"
	then
	rm -f "$GIT_INDEX_FILE"
	else
	echo >&2 "$err"
	false
	fi
	}
	esac \|\| die "Could not initialize the index"

	GIT_COMMIT=$commit
	export GIT_COMMIT
	git cat-file commit "$commit" >../commit \|\|
	die "Cannot read commit $commit"

	eval "$(set_ident <../commit)" \|\|
	die "setting author/committer failed for commit $commit"
	eval "$filter_env" < /dev/null \|\|
	die "env filter failed: $filter_env"

	if [ "$filter_tree" ]; then
	git checkout-index -f -u -a \|\|
	die "Could not checkout the index"
	# files that $commit removed are now still in the working tree;
	# remove them, else they would be added again
	git clean -d -q -f -x
	eval "$filter_tree" < /dev/null \|\|
	die "tree filter failed: $filter_tree"

	(
	git diff-index -r --name-only --ignore-submodules $commit -- &&
	git ls-files --others
	) > "$tempdir"/tree-state \|\| exit
	git update-index --add --replace --remove --stdin \
	< "$tempdir"/tree-state \|\| exit
	fi

	eval "$filter_index" < /dev/null \|\|
	die "index filter failed: $filter_index"

	parentstr=
	for parent in $parents; do
	for reparent in $(map "$parent"); do
	case "$parentstr " in
	" -p $reparent ")
	;;
	*)
	parentstr="$parentstr -p $reparent"
	;;
	esac
	done
	done
	if [ "$filter_parent" ]; then
	parentstr="$(echo "$parentstr" \| eval "$filter_parent")" \|\|
	die "parent filter failed: $filter_parent"
	fi

	{
	while IFS='' read -r header_line && test -n "$header_line"
	do
	# skip header lines...
	:;
	done
	# and output the actual commit message
	cat
	} <../commit \|
	eval "$filter_msg" > ../message \|\|
	die "msg filter failed: $filter_msg"

	if test -n "$need_index"
	then
	tree=$(git write-tree)
	else
	tree=$(git rev-parse "$commit^{tree}")
	fi
	workdir=$workdir @SHELL_PATH@ -c "$filter_commit" "git commit-tree" \
	"$tree" $parentstr < ../message > ../map/$commit \|\|
	die "could not write rewritten commit"
	done <../revs

	# If we are filtering for paths, as in the case of a subdirectory
	# filter, it is possible that a specified head is not in the set of
	# rewritten commits, because it was pruned by the revision walker.
	# Ancestor remapping fixes this by mapping these heads to the unique
	# nearest ancestor that survived the pruning.

	if test "$remap_to_ancestor" = t
	then
	while read ref
	do
	sha1=$(git rev-parse "$ref"^0)
	test -f "$workdir"/../map/$sha1 && continue
	ancestor=$(git rev-list --simplify-merges -1 "$ref" "$@")
	test "$ancestor" && echo $(map $ancestor) >> "$workdir"/../map/$sha1
	done < "$tempdir"/heads
	fi

	# Finally update the refs

	_x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
	_x40="$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40"
	echo
	while read ref
	do
	# avoid rewriting a ref twice
	test -f "$orig_namespace$ref" && continue

	sha1=$(git rev-parse "$ref"^0)
	rewritten=$(map $sha1)

	test $sha1 = "$rewritten" &&
	warn "WARNING: Ref '$ref' is unchanged" &&
	continue

	case "$rewritten" in
	'')
	echo "Ref '$ref' was deleted"
	git update-ref -m "filter-branch: delete" -d "$ref" $sha1 \|\|
	die "Could not delete $ref"
	;;
	$_x40)
	echo "Ref '$ref' was rewritten"
	if ! git update-ref -m "filter-branch: rewrite" \
	"$ref" $rewritten $sha1 2>/dev/null; then
	if test $(git cat-file -t "$ref") = tag; then
	if test -z "$filter_tag_name"; then
	warn "WARNING: You said to rewrite tagged commits, but not the corresponding tag."
	warn "WARNING: Perhaps use '--tag-name-filter cat' to rewrite the tag."
	fi
	else
	die "Could not rewrite $ref"
	fi
	fi
	;;
	*)
	# NEEDSWORK: possibly add -Werror, making this an error
	warn "WARNING: '$ref' was rewritten into multiple commits:"
	warn "$rewritten"
	warn "WARNING: Ref '$ref' points to the first one now."
	rewritten=$(echo "$rewritten" \| head -n 1)
	git update-ref -m "filter-branch: rewrite to first" \
	"$ref" $rewritten $sha1 \|\|
	die "Could not rewrite $ref"
	;;
	esac
	git update-ref -m "filter-branch: backup" "$orig_namespace$ref" $sha1 \|\|
	exit
	done < "$tempdir"/heads

	# TODO: This should possibly go, with the semantics that all positive given
	# refs are updated, and their original heads stored in refs/original/
	# Filter tags

	if [ "$filter_tag_name" ]; then
	git for-each-ref --format='%(objectname) %(objecttype) %(refname)' refs/tags \|
	while read sha1 type ref; do
	ref="${ref#refs/tags/}"
	# XXX: Rewrite tagged trees as well?
	if [ "$type" != "commit" -a "$type" != "tag" ]; then
	continue;
	fi

	if [ "$type" = "tag" ]; then
	# Dereference to a commit
	sha1t="$sha1"
	sha1="$(git rev-parse -q "$sha1"^{commit})" \|\| continue
	fi

	[ -f "../map/$sha1" ] \|\| continue
	new_sha1="$(cat "../map/$sha1")"
	GIT_COMMIT="$sha1"
	export GIT_COMMIT
	new_ref="$(echo "$ref" \| eval "$filter_tag_name")" \|\|
	die "tag name filter failed: $filter_tag_name"

	echo "$ref -> $new_ref ($sha1 -> $new_sha1)"

	if [ "$type" = "tag" ]; then
	new_sha1=$( ( printf 'object %s\ntype commit\ntag %s\n' \
	"$new_sha1" "$new_ref"
	git cat-file tag "$ref" \|
	sed -n \
	-e '1,/^$/{
	/^object /d
	/^type /d
	/^tag /d
	}' \
	-e '/^-----BEGIN PGP SIGNATURE-----/q' \
	-e 'p' ) \|
	git hash-object -t tag -w --stdin) \|\|
	die "Could not create new tag object for $ref"
	if git cat-file tag "$ref" \| \
	sane_grep '^-----BEGIN PGP SIGNATURE-----' >/dev/null 2>&1
	then
	warn "gpg signature stripped from tag object $sha1t"
	fi
	fi

	git update-ref "refs/tags/$new_ref" "$new_sha1" \|\|
	die "Could not write tag $new_ref"
	done
	fi

	unset GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE
	unset GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL GIT_AUTHOR_DATE
	unset GIT_COMMITTER_NAME GIT_COMMITTER_EMAIL GIT_COMMITTER_DATE
	test -z "$ORIG_GIT_DIR" \|\| {
	GIT_DIR="$ORIG_GIT_DIR" && export GIT_DIR
	}
	test -z "$ORIG_GIT_WORK_TREE" \|\| {
	GIT_WORK_TREE="$ORIG_GIT_WORK_TREE" &&
	export GIT_WORK_TREE
	}
	test -z "$ORIG_GIT_INDEX_FILE" \|\| {
	GIT_INDEX_FILE="$ORIG_GIT_INDEX_FILE" &&
	export GIT_INDEX_FILE
	}
	test -z "$ORIG_GIT_AUTHOR_NAME" \|\| {
	GIT_AUTHOR_NAME="$ORIG_GIT_AUTHOR_NAME" &&
	export GIT_AUTHOR_NAME
	}
	test -z "$ORIG_GIT_AUTHOR_EMAIL" \|\| {
	GIT_AUTHOR_EMAIL="$ORIG_GIT_AUTHOR_EMAIL" &&
	export GIT_AUTHOR_EMAIL
	}
	test -z "$ORIG_GIT_AUTHOR_DATE" \|\| {
	GIT_AUTHOR_DATE="$ORIG_GIT_AUTHOR_DATE" &&
	export GIT_AUTHOR_DATE
	}
	test -z "$ORIG_GIT_COMMITTER_NAME" \|\| {
	GIT_COMMITTER_NAME="$ORIG_GIT_COMMITTER_NAME" &&
	export GIT_COMMITTER_NAME
	}
	test -z "$ORIG_GIT_COMMITTER_EMAIL" \|\| {
	GIT_COMMITTER_EMAIL="$ORIG_GIT_COMMITTER_EMAIL" &&
	export GIT_COMMITTER_EMAIL
	}
	test -z "$ORIG_GIT_COMMITTER_DATE" \|\| {
	GIT_COMMITTER_DATE="$ORIG_GIT_COMMITTER_DATE" &&
	export GIT_COMMITTER_DATE
	}

	if test -n "$state_branch"
	then
	echo "Saving rewrite state to $state_branch" 1>&2
	state_blob=$(
	perl -e'opendir D, "../map" or die;
	open H, "\|-", "git hash-object -w --stdin" or die;
	foreach (sort readdir(D)) {
	next if m/^\.\.?$/;
	open F, "<../map/$_" or die;
	chomp($f = <F>);
	print H "$_:$f\n" or die;
	}
	close(H) or die;' \|\| die "Unable to save state")
	state_tree=$(/bin/echo -e "100644 blob $state_blob\tfilter.map" \| git mktree)
	if test -n "$state_commit"
	then
	state_commit=$(/bin/echo "Sync" \| git commit-tree "$state_tree" -p "$state_commit")
	else
	state_commit=$(/bin/echo "Sync" \| git commit-tree "$state_tree" )
	fi
	git update-ref "$state_branch" "$state_commit"
	fi

	cd "$orig_dir"
	rm -rf "$tempdir"

	trap - 0

	if [ "$(is_bare_repository)" = false ]; then
	git read-tree -u -m HEAD \|\| exit
	fi

	exit 0