hgmerge

add pretxncommit hook.

hook allows check of changeset after create, but before transaction
is committed.  hook failure rolls transaction back.

makes place for local policies like commit message must contain bug id
or reviewer signoff.

change also adds parent changeset ids to commit hook environment,
because is cheap and useful.

#!/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