hgmerge

Fix hg clone race with writer

Most read operations in hg don't need locks because we order reads and
writes for consistency. Clone is an exception to this as we're copying
entire file histories and could end up with more file history copied
than we have commits.

For now, make clone take a lock on the source repo. Non-hardlinked
clone should eventually be changed to use lockless pull.

#!/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

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

# Attempt to do a non-interactive merge
if type merge > /dev/null 2>&1; then
    merge "$LOCAL" "$BASE" "$OTHER" 2> /dev/null && exit 0
    cp "$LOCAL.orig" "$LOCAL"
elif type diff3 > /dev/null 2>&1; then
    diff3 -m "$LOCAL.orig" "$BASE" "$OTHER" > "$LOCAL" && exit 0
    cp "$LOCAL.orig" "$LOCAL"
fi

if [ -n "$DISPLAY" ]; then
    # try using kdiff3, which is fairly nice
    if type kdiff3 > /dev/null 2>&1; then
	kdiff3 --auto "$BASE" "$LOCAL" "$OTHER" -o "$LOCAL" || exit 1
	exit 0
    fi

    # try using tkdiff, which is a bit less sophisticated
    if type tkdiff > /dev/null 2>&1; then
	tkdiff "$LOCAL" "$OTHER" -a "$BASE" -o "$LOCAL" || exit 1
	exit 0
    fi
fi

# Attempt to do a merge with $EDITOR
if type merge > /dev/null 2>&1; then
    echo "conflicts detected in $LOCAL"
    merge "$LOCAL" "$BASE" "$OTHER" 2>/dev/null || $EDITOR "$LOCAL"
    exit 0
fi

if type diff3 > /dev/null 2>&1; then
    echo "conflicts detected in $LOCAL"
    diff3 -m "$LOCAL.orig" "$BASE" "$OTHER" > "$LOCAL" || $EDITOR "$LOCAL"
    exit 0
fi

HGTMP=""
cleanup_exit() {
    rm -rf "$HGTMP"
}

# attempt to manually merge with diff and patch
if type diff > /dev/null 2>&1 && type patch > /dev/null 2>&1; then
    # Remove temporary files even if we get interrupted
    trap "cleanup_exit" 0 # normal exit
    trap "exit 1" 1 2 3 6 15 # HUP INT QUIT ABRT TERM

    HGTMP="${TMPDIR-/tmp}/hgmerge.$RANDOM.$RANDOM.$RANDOM.$$"
    (umask 077 && mkdir "$HGTMP") || {
	echo "Could not create temporary directory! Exiting." 1>&2
	exit 1
    }

    diff -u "$BASE" "$OTHER" > "$HGTMP/diff"
    if patch "$LOCAL" < "$HGTMP/diff"; then
	exit 0
    else
	# If rejects are empty after using the editor, merge was ok
	$EDITOR "$LOCAL" "$LOCAL.rej" && test -s "$LOCAL.rej" || exit 0
    fi
    exit 1
fi

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