#!/bin/sh
#
# This program resolves merge conflicts in git
#
# Copyright (c) 2006 Theodore Y. Ts'o
#
# This file is licensed under the GPL v2, or a later version
# at the discretion of Junio C Hammano.
#

USAGE='[--tool=tool] [file to merge] ...'
SUBDIRECTORY_OK=Yes
. git-sh-setup
require_work_tree

# Returns true if the mode reflects a symlink
is_symlink () {
    test "$1" = 120000
}

local_present () {
    test -n "$local_mode"
}

remote_present () {
    test -n "$remote_mode"
}

base_present () {
    test -n "$base_mode"
}

cleanup_temp_files () {
    if test "$1" = --save-backup ; then
        mv -- "$BACKUP" "$path.orig"
        rm -f -- "$LOCAL" "$REMOTE" "$BASE"
    else
        rm -f -- "$LOCAL" "$REMOTE" "$BASE" "$BACKUP"
    fi
}

describe_file () {
    mode="$1"
    branch="$2"
    file="$3"

    printf "    "
    if test -z "$mode"; then
        printf "'%s' was deleted" "$path"
    elif is_symlink "$mode" ; then
        printf "'%s' is a symlink containing '%s'" "$path" "$file"
    else
        if base_present; then
            printf "'%s' was created" "$path"
        else
            printf "'%s' was modified" "$path"
        fi
    fi
    echo " in the $branch branch"
}


resolve_symlink_merge () {
    while true; do
        printf "Use (r)emote or (l)ocal, or (a)bort? "
        read ans
        case "$ans" in
            [lL]*)
                git-checkout-index -f --stage=2 -- "$path"
                git-add -- "$path"
                cleanup_temp_files --save-backup
                return
                ;;
            [rR]*)
                git-checkout-index -f --stage=3 -- "$path"
                git-add -- "$path"
                cleanup_temp_files --save-backup
                return
                ;;
            [aA]*)
                exit 1
                ;;
            esac
        done
}

resolve_deleted_merge () {
    while true; do
        printf "Use (m)odified or (d)eleted file, or (a)bort? "
        read ans
        case "$ans" in
            [mM]*)
                git-add -- "$path"
                cleanup_temp_files --save-backup
                return
                ;;
            [dD]*)
                git-rm -- "$path"
                cleanup_temp_files
                return
                ;;
            [aA]*)
                exit 1
                ;;
            esac
        done
}

check_unchanged () {
    if test "$path" -nt "$BACKUP" ; then
        status=0;
    else
        while true; do
            echo "$path seems unchanged."
            printf "Was the merge successful? [y/n] "
            read answer < /dev/tty
            case "$answer" in
                y*|Y*) status=0; break ;;
                n*|N*) status=1; break ;;
            esac
        done
    fi
}

save_backup () {
    if test "$status" -eq 0; then
        mv -- "$BACKUP" "$path.orig"
    fi
}

remove_backup () {
    if test "$status" -eq 0; then
        rm "$BACKUP"
    fi
}

merge_file () {
    path="$1"

    f=`git-ls-files -u -- "$path"`
    if test -z "$f" ; then
        if test ! -f "$path" ; then
            echo "$path: file not found"
        else
            echo "$path: file does not need merging"
        fi
        exit 1
    fi

    BACKUP="$path.BACKUP.$$"
    LOCAL="$path.LOCAL.$$"
    REMOTE="$path.REMOTE.$$"
    BASE="$path.BASE.$$"

    mv -- "$path" "$BACKUP"
    cp -- "$BACKUP" "$path"

    base_mode=`git ls-files -u -- "$path" | awk '{if ($3==1) print $1;}'`
    local_mode=`git ls-files -u -- "$path" | awk '{if ($3==2) print $1;}'`
    remote_mode=`git ls-files -u -- "$path" | awk '{if ($3==3) print $1;}'`

    base_present   && git cat-file blob ":1:$path" > "$BASE" 2>/dev/null
    local_present  && git cat-file blob ":2:$path" > "$LOCAL" 2>/dev/null
    remote_present && git cat-file blob ":3:$path" > "$REMOTE" 2>/dev/null

    if test -z "$local_mode" -o -z "$remote_mode"; then
        echo "Deleted merge conflict for $path:"
        describe_file "$local_mode" "local" "$LOCAL"
        describe_file "$remote_mode" "remote" "$REMOTE"
        resolve_deleted_merge
        return
    fi

    if is_symlink "$local_mode" || is_symlink "$remote_mode"; then
        echo "Symlink merge conflict for $path:"
        describe_file "$local_mode" "local" "$LOCAL"
        describe_file "$remote_mode" "remote" "$REMOTE"
        resolve_symlink_merge
        return
    fi

    echo "Normal merge conflict for $path:"
    describe_file "$local_mode" "local" "$LOCAL"
    describe_file "$remote_mode" "remote" "$REMOTE"
    printf "Hit return to start merge resolution tool (%s): " "$merge_tool"
    read ans

    case "$merge_tool" in
        kdiff3)
            if base_present ; then
                (kdiff3 --auto --L1 "$path (Base)" -L2 "$path (Local)" --L3 "$path (Remote)" \
                    -o "$path" -- "$BASE" "$LOCAL" "$REMOTE" > /dev/null 2>&1)
            else
                (kdiff3 --auto -L1 "$path (Local)" --L2 "$path (Remote)" \
                    -o "$path" -- "$LOCAL" "$REMOTE" > /dev/null 2>&1)
            fi
            status=$?
            remove_backup
            ;;
        tkdiff)
            if base_present ; then
                tkdiff -a "$BASE" -o "$path" -- "$LOCAL" "$REMOTE"
            else
                tkdiff -o "$path" -- "$LOCAL" "$REMOTE"
            fi
            status=$?
            save_backup
            ;;
        meld|vimdiff)
            touch "$BACKUP"
            $merge_tool -- "$LOCAL" "$path" "$REMOTE"
            check_unchanged
            save_backup
            ;;
        xxdiff)
            touch "$BACKUP"
            if base_present ; then
                xxdiff -X --show-merged-pane \
                    -R 'Accel.SaveAsMerged: "Ctrl-S"' \
                    -R 'Accel.Search: "Ctrl+F"' \
                    -R 'Accel.SearchForward: "Ctrl-G"' \
                    --merged-file "$path" -- "$LOCAL" "$BASE" "$REMOTE"
            else
                xxdiff -X --show-merged-pane \
                    -R 'Accel.SaveAsMerged: "Ctrl-S"' \
                    -R 'Accel.Search: "Ctrl+F"' \
                    -R 'Accel.SearchForward: "Ctrl-G"' \
                    --merged-file "$path" -- "$LOCAL" "$REMOTE"
            fi
            check_unchanged
            save_backup
            ;;
        opendiff)
            touch "$BACKUP"
            if base_present; then
                opendiff "$LOCAL" "$REMOTE" -ancestor "$BASE" -merge "$path" | cat
            else
                opendiff "$LOCAL" "$REMOTE" -merge "$path" | cat
            fi
            check_unchanged
            save_backup
            ;;
        emerge)
            if base_present ; then
                emacs -f emerge-files-with-ancestor-command "$LOCAL" "$REMOTE" "$BASE" "$path"
            else
                emacs -f emerge-files-command "$LOCAL" "$REMOTE" "$path"
            fi
            status=$?
            save_backup
            ;;
    esac
    if test "$status" -ne 0; then
        echo "merge of $path failed" 1>&2
        mv -- "$BACKUP" "$path"
        exit 1
    fi
    git add -- "$path"
    cleanup_temp_files
}

while case $# in 0) break ;; esac
do
    case "$1" in
        -t|--tool*)
            case "$#,$1" in
                *,*=*)
                    merge_tool=`expr "z$1" : 'z-[^=]*=\(.*\)'`
                    ;;
                1,*)
                    usage ;;
                *)
                    merge_tool="$2"
                    shift ;;
            esac
            ;;
        --)
            break
            ;;
        -*)
            usage
            ;;
        *)
            break
            ;;
    esac
    shift
done

if test -z "$merge_tool"; then
    merge_tool=`git-config merge.tool`
    case "$merge_tool" in
        kdiff3 | tkdiff | xxdiff | meld | opendiff | emerge | vimdiff | "")
            ;; # happy
        *)
            echo >&2 "git config option merge.tool set to unknown tool: $merge_tool"
            echo >&2 "Resetting to default..."
            unset merge_tool
            ;;
    esac
fi

if test -z "$merge_tool" ; then
    if type kdiff3 >/dev/null 2>&1 && test -n "$DISPLAY"; then
        merge_tool="kdiff3";
    elif type tkdiff >/dev/null 2>&1 && test -n "$DISPLAY"; then
        merge_tool=tkdiff
    elif type xxdiff >/dev/null 2>&1 && test -n "$DISPLAY"; then
        merge_tool=xxdiff
    elif type meld >/dev/null 2>&1 && test -n "$DISPLAY"; then
        merge_tool=meld
    elif type opendiff >/dev/null 2>&1; then
        merge_tool=opendiff
    elif type emacs >/dev/null 2>&1; then
        merge_tool=emerge
    elif type vimdiff >/dev/null 2>&1; then
        merge_tool=vimdiff
    else
        echo "No available merge resolution programs available."
        exit 1
    fi
fi

case "$merge_tool" in
    kdiff3|tkdiff|meld|xxdiff|vimdiff|opendiff)
        if ! type "$merge_tool" > /dev/null 2>&1; then
            echo "The merge tool $merge_tool is not available"
            exit 1
        fi
        ;;
    emerge)
        if ! type "emacs" > /dev/null 2>&1; then
            echo "Emacs is not available"
            exit 1
        fi
        ;;
    *)
        echo "Unknown merge tool: $merge_tool"
        exit 1
        ;;
esac

if test $# -eq 0 ; then
        files=`git ls-files -u | sed -e 's/^[^  ]*      //' | sort -u`
        if test -z "$files" ; then
                echo "No files need merging"
                exit 0
        fi
        echo Merging the files: $files
        git ls-files -u | sed -e 's/^[^ ]*      //' | sort -u | while read i
        do
                printf "\n"
                merge_file "$i" < /dev/tty > /dev/tty
        done
else
        while test $# -gt 0; do
                printf "\n"
                merge_file "$1"
                shift
        done
fi
exit 0