#!/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 "$3"
        else
                git commit-tree "$@"
        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"

# 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' \([^<]*\) <[^>]*> .*$/\1/
                        s/'\''/'\''\'\'\''/g
                        s/.*/GIT_'$uid'_NAME='\''&'\''; export GIT_'$uid'_NAME/p

                        g
                        s/^'$lid' [^<]* <\([^>]*\)> .*$/\1/
                        s/'\''/'\''\'\'\''/g
                        s/.*/GIT_'$uid'_EMAIL='\''&'\''; export GIT_'$uid'_EMAIL/p

                        g
                        s/^'$lid' [^<]* <[^>]*> \(.*\)$/\1/
                        s/'\''/'\''\'\'\''/g
                        s/.*/GIT_'$uid'_DATE='\''&'\''; export GIT_'$uid'_DATE/p

                        q
                }
        '

        LANG=C LC_ALL=C sed -ne "$pick_id_script"
        # Ensure non-empty id name.
        echo "case \"\$GIT_${uid}_NAME\" in \"\") GIT_${uid}_NAME=\"\${GIT_${uid}_EMAIL%%@*}\" && export GIT_${uid}_NAME;; esac"
}

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

OPTIONS_SPEC=
. git-sh-setup

if [ "$(is_bare_repository)" = false ]; then
        git diff-files --ignore-submodules --quiet &&
        git diff-index --cached --quiet HEAD -- ||
        die "Cannot rewrite branch(es) with a dirty working directory."
fi

tempdir=.git-rewrite
filter_env=
filter_tree=
filter_index=
filter_parent=
filter_msg=cat
filter_commit=
filter_tag_name=
filter_subdir=
orig_namespace=refs/original/
force=
prune_empty=
while :
do
        case "$1" in
        --)
                shift
                break
                ;;
        --force|-f)
                shift
                force=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"
                ;;
        --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"
                ;;
        --subdirectory-filter)
                filter_subdir="$OPTARG"
                ;;
        --original)
                orig_namespace=$(expr "$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 --filter-commit at the same time"
esac

case "$force" in
t)
        rm -rf "$tempdir"
;;
'')
        test -d "$tempdir" &&
                die "$tempdir already exists, please remove it"
esac
mkdir -p "$tempdir/t" &&
tempdir="$(cd "$tempdir"; pwd)" &&
cd "$tempdir/t" &&
workdir="$(pwd)" ||
die ""

# Remove tempdir on exit
trap 'cd ../..; rm -rf "$tempdir"' 0

ORIG_GIT_DIR="$GIT_DIR"
ORIG_GIT_WORK_TREE="$GIT_WORK_TREE"
ORIG_GIT_INDEX_FILE="$GIT_INDEX_FILE"
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 "Which ref do you want to rewrite?"

GIT_INDEX_FILE="$(pwd)/../index"
export GIT_INDEX_FILE
git read-tree || die "Could not seed the index"

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

case "$filter_subdir" in
"")
        git rev-list --reverse --topo-order --default HEAD \
                --parents --simplify-merges "$@"
        ;;
*)
        git rev-list --reverse --topo-order --default HEAD \
                --parents --simplify-merges "$@" -- "$filter_subdir"
esac > ../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

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

        case "$filter_subdir" in
        "")
                git read-tree -i -m $commit
                ;;
        *)
                # The commit may not have the subdirectory at all
                err=$(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 AUTHOR <../commit)" ||
                die "setting author failed for commit $commit"
        eval "$(set_ident COMMITTER <../commit)" ||
                die "setting 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 $commit &&
                        git ls-files --others
                ) > "$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
                        parentstr="$parentstr -p $reparent"
                done
        done
        if [ "$filter_parent" ]; then
                parentstr="$(echo "$parentstr" | eval "$filter_parent")" ||
                                die "parent filter failed: $filter_parent"
        fi

        sed -e '1,/^$/d' <../commit | \
                eval "$filter_msg" > ../message ||
                        die "msg filter failed: $filter_msg"
        @SHELL_PATH@ -c "$filter_commit" "git commit-tree" \
                $(git write-tree) $parentstr < ../message > ../map/$commit ||
                        die "could not write rewritten commit"
done <../revs

# In 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.  Fix it by mapping these heads to the unique nearest
# ancestor that survived the pruning.

if test "$filter_subdir"
then
        while read ref
        do
                sha1=$(git rev-parse "$ref"^0)
                test -f "$workdir"/../map/$sha1 && continue
                ancestor=$(git rev-list --simplify-merges -1 \
                                $ref -- "$filter_subdir")
                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="$(git rev-parse "$sha1"^{commit} 2>/dev/null)" || 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 mktag) ||
                                die "Could not create new tag object for $ref"
                        if git cat-file tag "$ref" | \
                           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

cd ../..
rm -rf "$tempdir"

trap - 0

unset GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE
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
}

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

exit 0