contrib/packagelib.sh

extensions: show traceback on load failure if --traceback flag is set

Before this patch, there was no handy way to investigate the reason why
extension couldn't be loaded.

If ui.debug is set, tracebacks of both "hgext.foo" and "foo" are displayed
because the first ImportError could occur at very deep dependency module.

gethgversion() {
    make clean
    make local || make local PURE=--pure
    HG="$PWD/hg"

    $HG version > /dev/null || { echo 'abort: hg version failed!'; exit 1 ; }

    hgversion=`$HG version | sed -ne 's/.*(version \(.*\))$/\1/p'`

    if echo $hgversion | grep -- '-' > /dev/null 2>&1; then
        # nightly build case, version is like 1.3.1+250-20b91f91f9ca
        version=`echo $hgversion | cut -d- -f1`
        release=`echo $hgversion | cut -d- -f2 | sed -e 's/+.*//'`
    else
        # official tag, version is like 1.3.1
        version=`echo $hgversion | sed -e 's/+.*//'`
        release='0'
    fi
}