hgmerge

mdiff: reinstate new algorithm

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mdiff: reinstate new algorithm

This unreverts the new algorithm with a fix from Chris (s/len/lena)
and adds some comments on what it's doing.

manifest hash: 75fc1acee1926e57d495f67a44cd88d9555f2356
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#!/bin/bash
#
# 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

EDITOR="${EDITOR:-vi}"

# Back up our file
cp $LOCAL $LOCAL.orig

# Attempt to do a non-interactive merge
if which merge > /dev/null ; then
    if merge $LOCAL $BASE $OTHER 2> /dev/null; then
	# success!
	exit 0
    fi
    cp $LOCAL.orig $LOCAL
elif which diff3 > /dev/null ; then
    if diff3 -m $LOCAL.orig $BASE $OTHER > $LOCAL ; then
	# success
	exit 0
    fi
    cp $LOCAL.orig $LOCAL
fi

if [ -n "$DISPLAY" ]; then
    # try using kdiff3, which is fairly nice
    if which kdiff3 > /dev/null ; then
	if kdiff3 --auto $BASE $LOCAL $OTHER -o $LOCAL ; then
	    exit 0
	else
	    exit 1
	fi
    fi

    # try using tkdiff, which is a bit less sophisticated
    if which tkdiff > /dev/null ; then
	if tkdiff $LOCAL $OTHER -a $BASE -o $LOCAL ; then
	    exit 0
	else
	    exit 1
	fi
    fi
fi

# Attempt to do a merge with $EDITOR
if which merge > /dev/null ; then
    echo "conflicts detected in $LOCAL"
    merge $LOCAL $BASE $OTHER 2>/dev/null || $EDITOR $LOCAL
    exit 0
fi

if which diff3 > /dev/null ; then
    echo "conflicts detected in $LOCAL"
    diff3 -m $LOCAL.orig $BASE $OTHER > $LOCAL || $EDITOR $LOCAL
    exit 0
fi

# attempt to manually merge with diff and patch
if which diff > /dev/null ; then
    if which patch > /dev/null ; then
	T=`mktemp`
	diff -u $BASE $OTHER > $T
	if patch $LOCAL < $T ; then
	    exit 0
	else
	    $EDITOR $LOCAL $LOCAL.rej
	fi
	rm $T
	exit 1
    fi
fi

echo "hgmerge: unable to find merge, tkdiff, kdiff3, or diff+patch!"
exit 1