#!/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 Hamano.
#

USAGE='[--tool=tool] [file to merge] ...'
SUBDIRECTORY_OK=Yes
OPTIONS_SPEC=
. git-sh-setup
require_work_tree
prefix=$(git rev-parse --show-prefix)

# 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 "  {%s}: " "$branch"
    if test -z "$mode"; then
        echo "deleted"
    elif is_symlink "$mode" ; then
        echo "a symbolic link -> '$(cat "$file")'"
    else
        if base_present; then
            echo "modified"
        else
            echo "created"
        fi
    fi
}


resolve_symlink_merge () {
    while true; do
        printf "Use (l)ocal or (r)emote, 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
        if base_present; then
            printf "Use (m)odified or (d)eleted file, or (a)bort? "
        else
            printf "Use (c)reated or (d)eleted file, or (a)bort? "
        fi
        read ans
        case "$ans" in
            [mMcC]*)
                git add -- "$path"
                cleanup_temp_files --save-backup
                return
                ;;
            [dD]*)
                git rm -- "$path" > /dev/null
                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
}

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

    ext="$$$(expr "$path" : '.*\(\.[^/]*\)$')"
    BACKUP="$path.BACKUP.$ext"
    LOCAL="$path.LOCAL.$ext"
    REMOTE="$path.REMOTE.$ext"
    BASE="$path.BASE.$ext"

    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:$prefix$path" >"$BASE" 2>/dev/null
    local_present  && git cat-file blob ":2:$prefix$path" >"$LOCAL" 2>/dev/null
    remote_present && git cat-file blob ":3:$prefix$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 "Symbolic link 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 "$merge_tool" in
        kdiff3)
            if base_present ; then
                ("$merge_tool_path" --auto --L1 "$path (Base)" --L2 "$path (Local)" --L3 "$path (Remote)" \
                    -o "$path" -- "$BASE" "$LOCAL" "$REMOTE" > /dev/null 2>&1)
            else
                ("$merge_tool_path" --auto --L1 "$path (Local)" --L2 "$path (Remote)" \
                    -o "$path" -- "$LOCAL" "$REMOTE" > /dev/null 2>&1)
            fi
            status=$?
            ;;
        tkdiff)
            if base_present ; then
                "$merge_tool_path" -a "$BASE" -o "$path" -- "$LOCAL" "$REMOTE"
            else
                "$merge_tool_path" -o "$path" -- "$LOCAL" "$REMOTE"
            fi
            status=$?
            ;;
        meld|vimdiff)
            touch "$BACKUP"
            "$merge_tool_path" -- "$LOCAL" "$path" "$REMOTE"
            check_unchanged
            ;;
        gvimdiff)
            touch "$BACKUP"
            "$merge_tool_path" -f -- "$LOCAL" "$path" "$REMOTE"
            check_unchanged
            ;;
        xxdiff)
            touch "$BACKUP"
            if base_present ; then
                "$merge_tool_path" -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
                "$merge_tool_path" -X --show-merged-pane \
                    -R 'Accel.SaveAsMerged: "Ctrl-S"' \
                    -R 'Accel.Search: "Ctrl+F"' \
                    -R 'Accel.SearchForward: "Ctrl-G"' \
                    --merged-file "$path" -- "$LOCAL" "$REMOTE"
            fi
            check_unchanged
            ;;
        opendiff)
            touch "$BACKUP"
            if base_present; then
                "$merge_tool_path" "$LOCAL" "$REMOTE" -ancestor "$BASE" -merge "$path" | cat
            else
                "$merge_tool_path" "$LOCAL" "$REMOTE" -merge "$path" | cat
            fi
            check_unchanged
            ;;
        ecmerge)
            touch "$BACKUP"
            if base_present; then
                "$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" --mode=merge3 --to="$path"
            else
                "$merge_tool_path" "$LOCAL" "$REMOTE" --mode=merge2 --to="$path"
            fi
            check_unchanged
            ;;
        emerge)
            if base_present ; then
                "$merge_tool_path" -f emerge-files-with-ancestor-command "$LOCAL" "$REMOTE" "$BASE" "$(basename "$path")"
            else
                "$merge_tool_path" -f emerge-files-command "$LOCAL" "$REMOTE" "$(basename "$path")"
            fi
            status=$?
            ;;
    esac
    if test "$status" -ne 0; then
        echo "merge of $path failed" 1>&2
        mv -- "$BACKUP" "$path"
        exit 1
    fi

    if test "$merge_keep_backup" = "true"; then
        mv -- "$BACKUP" "$path.orig"
    else
        rm -- "$BACKUP"
    fi

    git add -- "$path"
    cleanup_temp_files
}

while test $# != 0
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

valid_tool() {
        case "$1" in
                kdiff3 | tkdiff | xxdiff | meld | opendiff | emerge | vimdiff | gvimdiff | ecmerge)
                        ;; # happy
                *)
                        return 1
                        ;;
        esac
}

init_merge_tool_path() {
        merge_tool_path=`git config mergetool.$1.path`
        if test -z "$merge_tool_path" ; then
                case "$1" in
                        emerge)
                                merge_tool_path=emacs
                                ;;
                        *)
                                merge_tool_path=$1
                                ;;
                esac
        fi
}


if test -z "$merge_tool"; then
    merge_tool=`git config merge.tool`
    if test -n "$merge_tool" && ! valid_tool "$merge_tool"; then
            echo >&2 "git config option merge.tool set to unknown tool: $merge_tool"
            echo >&2 "Resetting to default..."
            unset merge_tool
    fi
fi

if test -z "$merge_tool" ; then
    if test -n "$DISPLAY"; then
        merge_tool_candidates="kdiff3 tkdiff xxdiff meld gvimdiff"
        if test -n "$GNOME_DESKTOP_SESSION_ID" ; then
            merge_tool_candidates="meld $merge_tool_candidates"
        fi
        if test "$KDE_FULL_SESSION" = "true"; then
            merge_tool_candidates="kdiff3 $merge_tool_candidates"
        fi
    fi
    if echo "${VISUAL:-$EDITOR}" | grep 'emacs' > /dev/null 2>&1; then
        merge_tool_candidates="$merge_tool_candidates emerge"
    fi
    if echo "${VISUAL:-$EDITOR}" | grep 'vim' > /dev/null 2>&1; then
        merge_tool_candidates="$merge_tool_candidates vimdiff"
    fi
    merge_tool_candidates="$merge_tool_candidates opendiff emerge vimdiff"
    echo "merge tool candidates: $merge_tool_candidates"
    for i in $merge_tool_candidates; do
        init_merge_tool_path $i
        if type "$merge_tool_path" > /dev/null 2>&1; then
            merge_tool=$i
            break
        fi
    done
    if test -z "$merge_tool" ; then
        echo "No known merge resolution program available."
        exit 1
    fi
else
    if ! valid_tool "$merge_tool"; then
        echo >&2 "Unknown merge_tool $merge_tool"
        exit 1
    fi

    init_merge_tool_path "$merge_tool"

    merge_keep_backup="$(git config --bool merge.keepBackup || echo true)"

    if ! type "$merge_tool_path" > /dev/null 2>&1; then
        echo "The merge tool $merge_tool is not available as '$merge_tool_path'"
        exit 1
    fi
fi


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: "$files"
        git ls-files -u |
        sed -e 's/^[^   ]*      //' |
        sort -u |
        while IFS= read i
        do
                printf "\n"
                merge_file "$i" < /dev/tty > /dev/tty
        done
else
        while test $# -gt 0; do
                printf "\n"
                merge_file "$1"
                shift
        done
fi
exit 0