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

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

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

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