Prolegomenon to any future tg-buildpackage

So I have been getting used to madduck's workflow for topgit and debian packaging, and one thing that bugged me a bit was all the steps required to to build. I tend to build quite a lot when debugging, so I wrote up a quick and dirty script to

export a copy of the master branch somewhere
export the patches from topgit
invoke debuild

I don't claim this is anywhere ready production quality, but maybe it helps someone.

Assumptions (that I remember)

you use the workflow above
you use pristine tar for your original tarballs
you invoke the script (I call it tg-debuild) from somewhere in your work tree

Here is the actual script:

    #!/bin/sh

    set -x

    if [ x$1 = x-k ]; then
        keep=1
    else
        keep=0
    fi

    WORKROOT=/tmp
    WORKDIR=`mktemp -d $WORKROOT/tg-debuild-XXXX`
    # yes, this could be nicer
    SOURCEPKG=`dpkg-parsechangelog | grep ^Source: | sed 's/^Source:\s*//'`
    UPSTREAM=`dpkg-parsechangelog | grep ^Version: | sed -e 's/^Version:\s*//' -e s/-[^-]*//`
    ORIG=$WORKDIR/${SOURCEPKG}_${UPSTREAM}.orig.tar.gz

    pristine-tar checkout $ORIG

    WORKTREE=$WORKDIR/$SOURCEPKG-$UPSTREAM

    CDUP=`git rev-parse --show-cdup`
    GDPATH=$PWD/$CDUP/.git

    DEST=$PWD/$CDUP/../build-area

    git archive --prefix=$WORKTREE/ --format=tar master | tar xfP -
    GIT_DIR=$GDPATH make -C $WORKTREE -f debian/rules tg-export
    cd $WORKTREE && GIT_DIR=$GDPATH debuild 
    if [ $?==0 -a -d $DEST ]; then
        cp $WORKDIR/*.deb $WORKDIR/*.dsc $WORKDIR/*.diff.gz $WORKDIR/*.changes $DEST
    fi


    if [ $keep = 0 ]; then
        rm -fr $WORKDIR
    fi