#!/bin/sh

#

# hgmerge - default merge helper for Mercurial

#

# This tries to find a way to do three-way merge on the current system.

# The result ought to end up in $1.

set -e # bail out quickly on failure

LOCAL="$1"

BASE="$2"

OTHER="$3"

if [ -z "$EDITOR" ]; then

    EDITOR="vi"

fi

# find decent versions of our utilities, insisting on the GNU versions where we

# need to

MERGE=merge

DIFF3=gdiff3

DIFF=gdiff

PATCH=gpatch

type $MERGE >/dev/null 2>&1 || MERGE=

type $DIFF3 >/dev/null 2>&1 || DIFF3=diff3

type $DIFF  >/dev/null 2>&1 || DIFF=diff

type $PATCH >/dev/null 2>&1 || PATCH=patch

$DIFF3 --version >/dev/null 2>&1 || DIFF3=

# find optional visual utilities

FILEMERGE='/Developer/Applications/Utilities/FileMerge.app/Contents/MacOS/FileMerge'

KDIFF3=kdiff3

TKDIFF=tkdiff

type $FILEMERGE >/dev/null 2>&1 || FILEMERGE=

type $KDIFF3    >/dev/null 2>&1 || KDIFF3=

type $TKDIFF    >/dev/null 2>&1 || TKDIFF=

# random part of names

RAND="$RANDOM.$RANDOM.$RANDOM.$$"

# temporary directory for diff+patch merge

HGTMP="${TMPDIR-/tmp}/hgmerge.$RAND"

# backup file

BACKUP="$LOCAL.orig.$RAND"

# file used to test for file change

CHGTEST="$LOCAL.chg.$RAND"

# put all your required cleanup here

cleanup() {

    rm -f "$BACKUP" "$CHGTEST"

    rm -rf "$HGTMP"

}

# functions concerning program exit

success() {

    cleanup

    exit 0

}

failure() {

    echo "merge failed" 1>&2

    mv "$BACKUP" "$LOCAL"

    cleanup

    exit 1

}

# Clean up when interrupted

trap "failure" 1 2 3 6 15 # HUP INT QUIT ABRT TERM

# Back up our file (and try hard to keep the mtime unchanged)

mv "$LOCAL" "$BACKUP"

cp "$BACKUP" "$LOCAL"

# Attempt to do a non-interactive merge

if [ -n "$MERGE" ]; then

    $MERGE "$LOCAL" "$BASE" "$OTHER" 2> /dev/null && success

    cp "$BACKUP" "$LOCAL"

elif [ -n "$DIFF3" ]; then

    echo $DIFF3 -m "$BACKUP" "$BASE" "$OTHER"

    $DIFF3 -m "$BACKUP" "$BASE" "$OTHER" > "$LOCAL" && success

    if [ $? -eq 2 ]; then

        echo "$DIFF3 failed! Exiting." 1>&2

        cp "$BACKUP" "$LOCAL"

        failure

    fi

    cp "$BACKUP" "$LOCAL"

fi

# on MacOS X try FileMerge.app, shipped with Apple's developer tools

if [ -n "$FILEMERGE" ]; then

    cp "$BACKUP" "$LOCAL"

    cp "$BACKUP" "$CHGTEST"

    # filemerge prefers the right by default

    $FILEMERGE -left "$OTHER" -right "$LOCAL" -ancestor "$BASE" -merge "$LOCAL"

    [ $? -ne 0 ] && echo "FileMerge failed to launch" && failure

    if test "$LOCAL" -nt "$CHGTEST"

    then

        success

    else

        echo "$LOCAL seems unchanged. Was the merge successful?"

        select answer in yes no

        do

            test "$answer" == "yes" && success || failure

        done

    fi

    failure

fi

if [ -n "$DISPLAY" ]; then

    # try using kdiff3, which is fairly nice

    if [ -n "$KDIFF3" ]; then

	$KDIFF3 --auto "$BASE" "$LOCAL" "$OTHER" -o "$LOCAL" || failure

	success

    fi

    # try using tkdiff, which is a bit less sophisticated

    if [ -n "$TKDIFF" ]; then

	$TKDIFF "$LOCAL" "$OTHER" -a "$BASE" -o "$LOCAL" || failure

	success

    fi

fi

# Attempt to do a merge with $EDITOR

if [ -n "$MERGE" ]; then

    echo "conflicts detected in $LOCAL"

    $MERGE "$LOCAL" "$BASE" "$OTHER" 2>/dev/null || $EDITOR "$LOCAL"

    success

fi

if [ -n "$DIFF3" ]; then

    echo "conflicts detected in $LOCAL"

    $DIFF3 -m "$BACKUP" "$BASE" "$OTHER" > "$LOCAL" || {

        case $? in

            1)

                $EDITOR "$LOCAL" ;;

            2)  echo "$DIFF3 failed! Exiting." 1>&2

                cp "$BACKUP" "$LOCAL"

                failure ;;

        esac

        success

    }

fi

# attempt to manually merge with diff and patch

if [ -n "$DIFF" -a -n "$PATCH" ]; then

    (umask 077 && mkdir "$HGTMP") || {

	echo "Could not create temporary directory $HGTMP" 1>&2

	failure

    }

    $DIFF -u "$BASE" "$OTHER" > "$HGTMP/diff" || :

    if $PATCH "$LOCAL" < "$HGTMP/diff"; then

	success

    else

	# If rejects are empty after using the editor, merge was ok

	$EDITOR "$LOCAL" "$LOCAL.rej" && test -s "$LOCAL.rej" || success

    fi

    failure

fi

echo "hgmerge: unable to find merge, tkdiff, kdiff3, or diff+patch!"

failure