#!/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.

set -e

USAGE="git-filter-branch [-d TEMPDIR] [FILTERS] DESTBRANCH [REV-RANGE]"
. git-sh-setup

map()
{
        # if it was not rewritten, take the original
        test -r "$workdir/../map/$1" || echo "$1"
        cat "$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%%@*}\""
}

tempdir=.git-rewrite
filter_env=
filter_tree=
filter_index=
filter_parent=
filter_msg=cat
filter_commit='git commit-tree "$@"'
filter_tag_name=
filter_subdir=
while case "$#" 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"
                ;;
        --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="$OPTARG"
                ;;
        --subdirectory-filter)
                filter_subdir="$OPTARG"
                ;;
        *)
                usage
                ;;
        esac
done

dstbranch="$1"
shift
test -n "$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 "$GIT_DIR" in
/*)
        ;;
*)
        GIT_DIR="$(pwd)/../../$GIT_DIR"
        ;;
esac
export GIT_DIR GIT_WORK_TREE=.

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

case "$filter_subdir" in
"")
        git rev-list --reverse --topo-order --default HEAD \
                --parents "$@"
        ;;
*)
        git rev-list --reverse --topo-order --default HEAD \
                --parents --full-history "$@" -- "$filter_subdir"
esac > ../revs
commits=$(cat ../revs | wc -l | tr -d " ")

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

i=0
while read commit parents; do
        i=$(($i+1))
        printf "$commit ($i/$commits) "

        case "$filter_subdir" in
        "")
                git read-tree -i -m $commit
                ;;
        *)
                git read-tree -i -m $commit:"$filter_subdir"
        esac

        export GIT_COMMIT=$commit
        git cat-file commit "$commit" >../commit

        eval "$(set_ident AUTHOR <../commit)"
        eval "$(set_ident COMMITTER <../commit)"
        eval "$filter_env" < /dev/null

        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" < /dev/null
                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" < /dev/null

        parentstr=
        for parent in $parents; do
                for reparent in $(map "$parent"); do
                        parentstr="$parentstr -p $reparent"
                done
        done
        if [ "$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

src_head=$(tail -n 1 ../revs | sed -e 's/ .*//')
target_head=$(head -n 1 ../map/$src_head)
case "$target_head" in
'')
        echo Nothing rewritten
        ;;
*)
        git update-ref refs/heads/"$dstbranch" $target_head
        if [ $(cat ../map/$src_head | 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 $dstbranch head but you will need to resolve the situation now (probably by manually merging the other commits). These are all the commits:" >&2
                sed 's/^/       /' ../map/$src_head >&2
                ret=1
        fi
        ;;
esac

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