Add git-filter-branch

This script is derived from Pasky's cg-admin-rewritehist.

In fact, it _is_ the same script, minimally adapted to work without cogito.
It _should_ be able to perform the same tasks, even if only relying on
core-git programs.

All the work is Pasky's, just the adaption is mine.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Hopefully-signed-off-by: Petr "cogito master" Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 430 insertions, 0 deletions

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
new file mode 100644
index 0000000000..0c8a7dfd3e
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@@ -0,0 +1,430 @@
+#!/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 GIT revision history by creating a new branch from
+# your current branch by applying custom filters on each revision.
+# Those filters can modify each tree (e.g. removing a file or running
+# a perl rewrite on all files) or information about each commit.
+# Otherwise, all information (including original commit times or merge
+# information) will be preserved.
+#
+# The command takes the new branch name as a mandatory argument and
+# the filters as optional arguments. If you specify no filters, the
+# commits will be recommitted without any changes, which would normally
+# have no effect and result with the new branch pointing to the same
+# branch as your current branch. (Nevertheless, this may be useful in
+# the future for compensating for some Git bugs or such, therefore
+# such a usage is permitted.)
+#
+# WARNING! The rewritten history will have different ids for all the
+# objects and will not converge with the original branch. You will not
+# be able to easily push and distribute the rewritten branch. Please do
+# not use this command if you do not know the full implications, and
+# avoid using it anyway - do not do what a simple single commit on top
+# of the current version would fix.
+#
+# Always verify that the rewritten version is correct before disposing
+# the original branch.
+#
+# Note that since this operation is extensively I/O expensive, it might
+# be a good idea to do it off-disk, e.g. on tmpfs. Reportedly the speedup
+# is very noticeable.
+#
+# OPTIONS
+# -------
+# -d TEMPDIR:: The path to the temporary tree used for rewriting
+#	When applying a tree filter, the command needs to temporary
+#	checkout the tree to some directory, which may consume
+#	considerable space in case of large projects. By default it
+#	does this in the '.git-rewrite/' directory but you can override
+#	that choice by this parameter.
+#
+# -r STARTREV:: The commit id to start the rewrite at
+#	Normally, the command will rewrite the entire history. If you
+#	pass this argument, though, this will be the first commit it
+#	will rewrite and keep the previous commits intact.
+#
+# -k KEEPREV:: A commit id until which _not_ to rewrite history
+#	If you pass this argument, this commit and all of its
+#	predecessors are kept intact.
+#
+# Filters
+# ~~~~~~~
+# The filters are applied in the order as listed below. The COMMAND
+# argument is always evaluated in shell using the 'eval' command.
+# The $GIT_COMMIT environment variable is permanently set to contain
+# the id of the commit being rewritten. The author/committer environment
+# variables are set before the first filter is run.
+#
+# A 'map' function is available that takes an "original sha1 id" argument
+# and outputs a "rewritten sha1 id" if the commit has been already
+# rewritten, fails otherwise; the 'map' function can return several
+# ids on separate lines if your commit filter emitted multiple commits
+# (see below).
+#
+# --env-filter COMMAND:: The filter for modifying environment
+#	This is the filter for modifying the environment in which
+#	the commit will be performed. Specifically, you might want
+#	to rewrite the author/committer name/email/time environment
+#	variables (see `git-commit` for details). Do not forget to
+#	re-export the variables.
+#
+# --tree-filter COMMAND:: The filter for rewriting tree (and its contents)
+#	This is the filter for rewriting the tree and its contents.
+#	The COMMAND argument is evaluated in shell with the working
+#	directory set to the root of the checked out tree. The new tree
+#	is then used as-is (new files are auto-added, disappeared files
+#	are auto-removed - .gitignore files nor any other ignore rules
+#	HAVE NO EFFECT!).
+#
+# --index-filter COMMAND:: The filter for rewriting index
+#	This is the filter for rewriting the Git's directory index.
+#	It is similar to the tree filter but does not check out the
+#	tree, which makes it much faster. However, you must use the
+#	lowlevel Git index manipulation commands to do your work.
+#
+# --parent-filter COMMAND:: The filter for rewriting parents
+#	This is the filter for rewriting the commit's parent list.
+#	It will receive the parent string on stdin and shall output
+#	the new parent string on stdout. The parent string is in
+#	format accepted by `git-commit-tree`: empty for initial
+#	commit, "-p parent" for a normal commit and "-p parent1
+#	-p parent2 -p parent3 ..." for a merge commit.
+#
+# --msg-filter COMMAND:: The filter for rewriting commit message
+#	This is the filter for rewriting the commit messages.
+#	The COMMAND argument is evaluated in shell with the original
+#	commit message on standard input; its standard output is
+#	is used as the new commit message.
+#
+# --commit-filter COMMAND:: The filter for performing the commit
+#	If this filter is passed, it will be called instead of the
+#	`git-commit-tree` command, with those arguments:
+#
+#		TREE_ID [-p PARENT_COMMIT_ID]...
+#
+#	and the log message on stdin. The commit id is expected on
+#	stdout. As a special extension, the commit filter may emit
+#	multiple commit ids; in that case, all of them will be used
+#	as parents instead of the original commit in further commits.
+#
+# --tag-name-filter COMMAND:: The filter for rewriting tag names.
+#	If this filter is passed, it will be called for every tag ref
+#	that points to a rewritten object (or to a tag object which
+#	points to a rewritten object). The original tag name is passed
+#	via standard input, and the new tag name is expected on standard
+#	output.
+#
+#	The original tags are not deleted, but can be overwritten;
+#	use "--tag-name-filter=cat" to simply update the tags. In this
+#	case, be very careful and make sure you have the old tags
+#	backed up in case the conversion has run afoul.
+#
+#	Note that there is currently no support for proper rewriting of
+#	tag objects; in layman terms, if the tag has a message or signature
+#	attached, the rewritten tag won't have it. Sorry. (It is by
+#	definition impossible to preserve signatures at any rate, though.)
+#
+# EXAMPLE USAGE
+# -------------
+# Suppose you want to remove a file (containing confidential information
+# or copyright violation) from all commits:
+#
+#	git-filter-branch --tree-filter 'rm filename' newbranch
+#
+# A significantly faster version:
+#
+#	git-filter-branch --index-filter 'git-update-index --remove filename' newbranch
+#
+# Now, you will get the rewritten history saved in the branch 'newbranch'
+# (your current branch is left untouched).
+#
+# To "etch-graft" a commit to the revision history (set a commit to be
+# the parent of the current initial commit and propagate that):
+#
+#	git-filter-branch --parent-filter sed\ 's/^$/-p graftcommitid/' newbranch
+#
+# (if the parent string is empty - therefore we are dealing with the
+# initial commit - add graftcommit as a parent). Note that this assumes
+# history with a single root (that is, no git-merge without common ancestors
+# happened). If this is not the case, use:
+#
+#	git-filter-branch --parent-filter 'cat; [ "$GIT_COMMIT" = "COMMIT" ] && echo "-p GRAFTCOMMIT"' newbranch
+#
+# To remove commits authored by "Darl McBribe" from the history:
+#
+#	git-filter-branch --commit-filter 'if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ]; then shift; while [ -n "$1" ]; do shift; echo "$1"; shift; done; else git-commit-tree "$@"; fi' newbranch
+#
+# (the shift magic first throws away the tree id and then the -p
+# parameters). Note that this handles merges properly! In case Darl
+# committed a merge between P1 and P2, it will be propagated properly
+# and all children of the merge will become merge commits with P1,P2
+# as their parents instead of the merge commit.
+#
+# To restrict rewriting to only part of the history, use -r or -k or both.
+# Consider this history:
+#
+#	     D--E--F--G--H
+#	    /     /
+#	A--B-----C
+#
+# To rewrite only commits F,G,H, use:
+#
+#	git-filter-branch -r F ...
+#
+# To rewrite commits E,F,G,H, use one of these:
+#
+#	git-filter-branch -r E -k C ...
+#	git-filter-branch -k D -k C ...
+
+# Testsuite: TODO
+
+set -e
+
+USAGE="git-filter-branch [-d TEMPDIR] [-r STARTREV]... [-k KEEPREV]... [-s SRCBRANCH] [FILTERS] DESTBRANCH"
+. git-sh-setup
+
+map()
+{
+	[ -r "$workdir/../map/$1" ] || return 1
+	cat "$workdir/../map/$1"
+}
+
+# When piped a commit, output a script to set the ident of either
+# "author" or "committer
+
+set_ident () {
+	lid="$(echo "$1" | tr "A-Z" "a-z")"
+	uid="$(echo "$1" | tr "a-z" "A-Z")"
+	pick_id_script='
+		/^'$lid' /{
+			s/'\''/'\''\\'\'\''/g
+			h
+			s/^'$lid' \([^<]*\) <[^>]*> .*$/\1/
+			s/'\''/'\''\'\'\''/g
+			s/.*/export GIT_'$uid'_NAME='\''&'\''/p
+
+			g
+			s/^'$lid' [^<]* <\([^>]*\)> .*$/\1/
+			s/'\''/'\''\'\'\''/g
+			s/.*/export GIT_'$uid'_EMAIL='\''&'\''/p
+
+			g
+			s/^'$lid' [^<]* <[^>]*> \(.*\)$/\1/
+			s/'\''/'\''\'\'\''/g
+			s/.*/export GIT_'$uid'_DATE='\''&'\''/p
+
+			q
+		}
+	'
+
+	LANG=C LC_ALL=C sed -ne "$pick_id_script"
+	# Ensure non-empty id name.
+	echo "[ -n \"\$GIT_${uid}_NAME\" ] || export GIT_${uid}_NAME=\"\${GIT_${uid}_EMAIL%%@*}\""
+}
+
+# list all parent's object names for a given commit
+get_parents () {
+	git-rev-list -1 --parents "$1" | sed "s/^[0-9a-f]*//"
+}
+
+tempdir=.git-rewrite
+unchanged=" "
+filter_env=
+filter_tree=
+filter_index=
+filter_parent=
+filter_msg=cat
+filter_commit='git-commit-tree "$@"'
+filter_tag_name=
+srcbranch=HEAD
+while case "$#" in 0) usage;; esac
+do
+	case "$1" in
+	--)
+		shift
+		break
+		;;
+	-*)
+		;;
+	*)
+		break;
+	esac
+
+	# all switches take one argument
+	ARG="$1"
+	case "$#" in 1) usage ;; esac
+	shift
+	OPTARG="$1"
+	shift
+
+	case "$ARG" in
+	-d)
+		tempdir="$OPTARG"
+		;;
+	-r)
+		unchanged="$(get_parents "$OPTARG") $unchanged"
+		;;
+	-k)
+		unchanged="$(git-rev-parse "$OPTARG"^{commit}) $unchanged"
+		;;
+	--env-filter)
+		filter_env="$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="$OPTARG"
+		;;
+	--tag-name-filter)
+		filter_tag_name="$OPTARG"
+		;;
+	-s)
+		srcbranch="$OPTARG"
+		;;
+	*)
+		usage
+		;;
+	esac
+done
+
+dstbranch="$1"
+test -n "$dstbranch" || die "missing branch name"
+git-show-ref "refs/heads/$dstbranch" 2> /dev/null &&
+	die "branch $dstbranch already exists"
+
+test ! -e "$tempdir" || die "$tempdir already exists, please remove it"
+mkdir -p "$tempdir/t"
+cd "$tempdir/t"
+workdir="$(pwd)"
+
+case "$GIT_DIR" in
+/*)
+	;;
+*)
+	export GIT_DIR="$(pwd)/../../$GIT_DIR"
+	;;
+esac
+
+export GIT_INDEX_FILE="$(pwd)/../index"
+git-read-tree # seed the index file
+
+ret=0
+
+
+mkdir ../map # map old->new commit ids for rewriting parents
+
+# seed with identity mappings for the parents where we start off
+for commit in $unchanged; do
+	echo $commit > ../map/$commit
+done
+
+git-rev-list --reverse --topo-order $srcbranch --not $unchanged >../revs
+commits=$(cat ../revs | wc -l | tr -d " ")
+
+test $commits -eq 0 && die "Found nothing to rewrite"
+
+i=0
+while read commit; do
+	i=$((i+1))
+	printf "$commit ($i/$commits) "
+
+	git-read-tree -i -m $commit
+
+	export GIT_COMMIT=$commit
+	git-cat-file commit "$commit" >../commit
+
+	eval "$(set_ident AUTHOR <../commit)"
+	eval "$(set_ident COMMITTER <../commit)"
+	eval "$filter_env"
+
+	if [ "$filter_tree" ]; then
+		git-checkout-index -f -u -a
+		# files that $commit removed are now still in the working tree;
+		# remove them, else they would be added again
+		git-ls-files -z --others | xargs -0 rm -f
+		eval "$filter_tree"
+		git-diff-index -r $commit | cut -f 2- | tr '\n' '\0' | \
+			xargs -0 git-update-index --add --replace --remove
+		git-ls-files -z --others | \
+			xargs -0 git-update-index --add --replace --remove
+	fi
+
+	eval "$filter_index"
+
+	parentstr=
+	for parent in $(get_parents $commit); do
+		if [ -r "../map/$parent" ]; then
+			for reparent in $(cat "../map/$parent"); do
+				parentstr="$parentstr -p $reparent"
+			done
+		else
+			die "assertion failed: parent $parent for commit $commit not found in rewritten ones"
+		fi
+	done
+	if [ "$filter_parent" ]; then
+		parentstr="$(echo "$parentstr" | eval "$filter_parent")"
+	fi
+
+	sed -e '1,/^$/d' <../commit | \
+		eval "$filter_msg" | \
+		sh -c "$filter_commit" git-commit-tree $(git-write-tree) $parentstr | \
+		tee ../map/$commit
+done <../revs
+
+git-update-ref refs/heads/"$dstbranch" $(head -n 1 ../map/$(tail -n 1 ../revs))
+if [ "$(cat ../map/$(tail -n 1 ../revs) | wc -l)" -gt 1 ]; then
+	echo "WARNING: Your commit filter caused the head commit to expand to several rewritten commits. Only the first such commit was recorded as the current $dstbranch head but you will need to resolve the situation now (probably by manually merging the other commits). These are all the commits:" >&2
+	sed 's/^/	/' ../map/$(tail -n 1 ../revs) >&2
+	ret=1
+fi
+
+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="$(git-rev-parse "$sha1"^{commit} 2>/dev/null)" || continue
+		fi
+
+		[ -f "../map/$sha1" ] || continue
+		new_sha1="$(cat "../map/$sha1")"
+		export GIT_COMMIT="$sha1"
+		new_ref="$(echo "$ref" | eval "$filter_tag_name")"
+
+		echo "$ref -> $new_ref ($sha1 -> $new_sha1)"
+
+		if [ "$type" = "tag" ]; then
+			# Warn that we are not rewriting the tag object itself.
+			warn "unreferencing tag object $sha1t"
+		fi
+
+		git-update-ref "refs/tags/$new_ref" "$new_sha1"
+	done
+fi
+
+cd ../..
+rm -rf "$tempdir"
+echo "Rewritten history saved to the $dstbranch branch"
+
+exit $ret