contrib/builddeb

revlog: remove unnecessary cache validation in _chunks

Previously, we likely called _chunkraw() multiple times in order to
ensure it didn't change out from under us. I'm pretty certain this code
had its origins in the days where we attempted to have thread safety of
localrepository and thus revlog instances.

revlog instances are already not thread safe for writing. And, as of
Mercurial 3.6, hgweb uses a separate localrepository instance per
request, so there should only be a single thread reading a revlog at
a time. We more or less decided that attempting to make classes like
revlog thread safe is a lost cause.

So, this patch removes thread safety from _chunks. As a result, we make
one less call into _chunkraw() when the initial read isn't serviced
by the cache. This translates to savings of 4 function calls overall
and possibly prevents the creation of an additional buffer view into the
cache. I doubt this translates into any real world performance wins
because decompression will almost certainly dwarf time spent in
_chunks(). But it does make the code simpler, so it is an improvement.

#!/bin/sh -e
#
# Build a Mercurial debian package from the current repo
#
# Tested on Jessie (stable as of original script authoring.)

. $(dirname $0)/packagelib.sh

BUILD=1
CLEANUP=1
DISTID=`(lsb_release -is 2> /dev/null | tr '[:upper:]' '[:lower:]') || echo debian`
CODENAME=`lsb_release -cs 2> /dev/null || echo unknown`
while [ "$1" ]; do
    case "$1" in
    --distid )
        shift
        DISTID="$1"
        shift
        ;;
    --codename )
        shift
        CODENAME="$1"
        shift
        ;;
    --cleanup )
        shift
        BUILD=
        ;;
    --build )
        shift
        CLEANUP=
        ;;
    * )
        echo "Invalid parameter $1!" 1>&2
        exit 1
        ;;
    esac
done

trap "if [ '$CLEANUP' ] ; then rm -r '$PWD/debian' ; fi" EXIT

set -u

if [ ! -d .hg ]; then
    echo 'You are not inside a Mercurial repository!' 1>&2
    exit 1
fi

gethgversion
debver="$version"
if [ -n "$type" ] ; then
    debver="$debver~$type"
fi
if [ -n "$distance" ] ; then
    debver="$debver+$distance-$node"
fi

control=debian/control
changelog=debian/changelog

if [ "$BUILD" ]; then
    if [ -d debian ] ; then
        echo "Error! debian control directory already exists!"
        exit 1
    fi

    cp -r $PWD/contrib/debian debian
    chmod -R 0755 debian

    # This looks like sed -i, but sed -i behaves just differently enough
    # between BSD and GNU sed that I gave up and did the dumb thing.
    sed "s/__VERSION__/$debver/" < $changelog > $changelog.tmp
    date=$(date --rfc-2822)
    sed "s/__DATE__/$date/" < $changelog.tmp > $changelog
    rm $changelog.tmp

    debuild -us -uc -b
    if [ $? != 0 ]; then
        echo 'debuild failed!'
        exit 1
    fi

fi
if [ "$CLEANUP" ] ; then
    echo
    OUTPUTDIR=${OUTPUTDIR:=packages/$DISTID-$CODENAME}
    mkdir -p "$OUTPUTDIR"
    find ../mercurial*.deb ../mercurial_*.build ../mercurial_*.changes \
          -type f -newer $control -print0 | \
      xargs -Inarf -0 mv narf "$OUTPUTDIR"
    echo "Built packages for $debver:"
    find "$OUTPUTDIR" -type f -newer $control -name '*.deb'
fi