hgmerge

Deal with failed clone/transaction interaction

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Deal with failed clone/transaction interaction

> What is happening is that something in the transaction machinery is
> causing the directory to be completely recreated.

The transaction gets rolled back by its destructor. This is critical
so it happens whenever an exception occurs that unwinds the stack.

Unfortunately, what's happening with clone is we're trying to delete
the directory during exception propagation. And a reference to the
transaction is held in the exception backtrace stack frames so it
still exists until the exception is completely resolved.

So there's no way to do the directory delete inside the exception
handling cleanly.

But we can handle it similarly to the transaction itself: use an
object with a destructor.

manifest hash: fc38550a20d64d08333f256bbedc312493c1390b
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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