#!/bin/sh
. git-sh-setup || dir "Not a git archive"

usage() {
    echo >&2 'usage: git bisect [start|bad|good|next|reset|visualize]
git bisect start                reset bisect state and start bisection.
git bisect bad [<rev>]          mark <rev> a known-bad revision.
git bisect good [<rev>...]      mark <rev>... known-good revisions.
git bisect next                 find next bisection to test and check it out.
git bisect reset [<branch>]     finish bisection search and go back to branch.
git bisect visualize            show bisect status in gitk.
git bisect replay <logfile>     replay bisection log
git bisect log                  show bisect log.'
    exit 1
}

bisect_autostart() {
        test -d "$GIT_DIR/refs/bisect" || {
                echo >&2 'You need to start by "git bisect start"'
                if test -t 0
                then
                        echo >&2 -n 'Do you want me to do it for you [Y/n]? '
                        read yesno
                        case "$yesno" in
                        [Nn]*)
                                exit ;;
                        esac
                        bisect_start
                else
                        exit 1
                fi
        }
}

bisect_start() {
        case "$#" in 0) ;; *) usage ;; esac
        #
        # Verify HEAD. If we were bisecting before this, reset to the
        # top-of-line master first!
        #
        head=$(readlink $GIT_DIR/HEAD) || die "Bad HEAD - I need a symlink"
        case "$head" in
        refs/heads/bisect*)
                git checkout master || exit
                ;;
        refs/heads/*)
                ;;
        *)
                die "Bad HEAD - strange symlink"
                ;;
        esac

        #
        # Get rid of any old bisect state
        #
        rm -f "$GIT_DIR/refs/heads/bisect"
        rm -rf "$GIT_DIR/refs/bisect/"
        mkdir "$GIT_DIR/refs/bisect"
        echo "git-bisect start" >"$GIT_DIR/BISECT_LOG"
}

bisect_bad() {
        bisect_autostart
        case "$#" in
        0)
                rev=$(git-rev-parse --verify HEAD) ;;
        1)
                rev=$(git-rev-parse --verify "$1") ;;
        *)
                usage ;;
        esac || exit
        echo "$rev" >"$GIT_DIR/refs/bisect/bad"
        echo "# bad: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
        echo "git-bisect bad $rev" >>"$GIT_DIR/BISECT_LOG"
        bisect_auto_next
}

bisect_good() {
        bisect_autostart
        case "$#" in
        0)    revs=$(git-rev-parse --verify HEAD) || exit ;;
        *)    revs=$(git-rev-parse --revs-only --no-flags "$@") &&
                test '' != "$revs" || die "Bad rev input: $@" ;;
        esac
        for rev in $revs
        do
                rev=$(git-rev-parse --verify "$rev") || exit
                echo "$rev" >"$GIT_DIR/refs/bisect/good-$rev"
                echo "# good: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
                echo "git-bisect good $rev" >>"$GIT_DIR/BISECT_LOG"
        done
        bisect_auto_next
}

bisect_next_check() {
        next_ok=no
        test -f "$GIT_DIR/refs/bisect/bad" &&
        case "$(cd "$GIT_DIR" && echo refs/bisect/good-*)" in
        refs/bisect/good-\*) ;;
        *) next_ok=yes ;;
        esac
        case "$next_ok,$1" in
        no,) false ;;
        no,fail)
            echo >&2 'You need to give me at least one good and one bad revisions.'
            exit 1 ;;
        *)
            true ;;
        esac
}

bisect_auto_next() {
        bisect_next_check && bisect_next || :
}

bisect_next() {
        case "$#" in 0) ;; *) usage ;; esac
        bisect_autostart
        bisect_next_check fail
        bad=$(git-rev-parse --verify refs/bisect/bad) &&
        good=$(git-rev-parse --sq --revs-only --not \
                $(cd "$GIT_DIR" && ls refs/bisect/good-*)) &&
        rev=$(eval "git-rev-list --bisect $good $bad") || exit
        if [ -z "$rev" ]; then
            echo "$bad was both good and bad"
            exit 1
        fi
        if [ "$rev" = "$bad" ]; then
            echo "$rev is first bad commit"
            git-diff-tree --pretty $rev
            exit 0
        fi
        nr=$(eval "git-rev-list $rev $good" | wc -l) || exit
        echo "Bisecting: $nr revisions left to test after this"
        echo "$rev" > "$GIT_DIR/refs/heads/new-bisect"
        git checkout new-bisect || exit
        mv "$GIT_DIR/refs/heads/new-bisect" "$GIT_DIR/refs/heads/bisect" &&
        ln -sf refs/heads/bisect "$GIT_DIR/HEAD"
        git-show-branch "$rev"
}

bisect_visualize() {
        bisect_next_check fail
        gitk bisect/bad --not `cd "$GIT_DIR/refs" && echo bisect/good-*`
}

bisect_reset() {
        case "$#" in
        0) branch=master ;;
        1) test -f "$GIT_DIR/refs/heads/$1" || {
               echo >&2 "$1 does not seem to be a valid branch"
               exit 1
           }
           branch="$1" ;;
        *)
            usage ;;
        esac
        git checkout "$branch" &&
        rm -fr "$GIT_DIR/refs/bisect"
        rm -f "$GIT_DIR/refs/heads/bisect"
        rm -f "$GIT_DIR/BISECT_LOG"
}

bisect_replay () {
        test -r "$1" || {
                echo >&2 "cannot read $1 for replaying"
                exit 1
        }
        bisect_reset
        while read bisect command rev
        do
                test "$bisect" = "git-bisect" || continue
                case "$command" in
                start)
                        bisect_start
                        ;;
                good)
                        echo "$rev" >"$GIT_DIR/refs/bisect/good-$rev"
                        echo "# good: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
                        echo "git-bisect good $rev" >>"$GIT_DIR/BISECT_LOG"
                        ;;
                bad)
                        echo "$rev" >"$GIT_DIR/refs/bisect/bad"
                        echo "# bad: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
                        echo "git-bisect bad $rev" >>"$GIT_DIR/BISECT_LOG"
                        ;;
                *)
                        echo >&2 "?? what are you talking about?"
                        exit 1 ;;
                esac
        done <"$1"
        bisect_auto_next
}

case "$#" in
0)
    usage ;;
*)
    cmd="$1"
    shift
    case "$cmd" in
    start)
        bisect_start "$@" ;;
    bad)
        bisect_bad "$@" ;;
    good)
        bisect_good "$@" ;;
    next)
        # Not sure we want "next" at the UI level anymore.
        bisect_next "$@" ;;
    visualize)
        bisect_visualize "$@" ;;
    reset)
        bisect_reset "$@" ;;
    replay)
        bisect_replay "$@" ;;
    log)
        cat "$GIT_DIR/BISECT_LOG" ;;
    *)
        usage ;;
    esac
esac