#!/bin/sh

set -eu
u="Ensure that BUILDDIR is an empty directory.
If BUILDDIR does not exist, create it.
If BUILDDIR does exist, delete all its contents.
To avoid deleting things accidentally, we refuse to delete BUILDDIR
unless it contains a file named 'this-is-a-nightly-build-dir'.  We
place a file by that name in directories we create."
eval "$(args wipe-build-tree builddir -- "$@")"

if [ -d $builddir ]; then
    if [ -f $builddir/this-is-a-nightly-build-dir ]; then
        # Don't delete and re-create the directory; delete its contents.
        # This way, if $builddir is a symlink (say, to a tree on another
        # filesystem), we don't break it.
        rm -rf $builddir/*
    else
        echo "error: $builddir does not seem to be a nightly build dir" >&2
        exit 1
    fi
else
    mkdir $builddir
fi
touch $builddir/this-is-a-nightly-build-dir