nixpkgs/pkgs/build-support/fetchmtn/builder.sh

if [ -e .attrs.sh ]; then source .attrs.sh; fi
source $stdenv/setup

set -x

if ! [ -f "$cacheDB" ]; then
    echo "Creating cache DB $cacheDB"
    mtn --db "$cacheDB" db init
fi

header "getting revision $selector";

done=;
for source in $dbs; do
    if mtn pull --db "$cacheDB" "$source" "${branch}"; then
        revision="$(mtn --db "$cacheDB" au toposort $(mtn --db "$cacheDB" au select "$selector") | tail -1)";
        if [ -n "$revision" ]; then
            if mtn --db "$cacheDB" au get_revision "$revision"; then
                echo "found revision $revision"
                done=1;
            else
                echo "revision $revision does not exist";
            fi
        else
            echo "selector $selector does not match any revision";
        fi
    else
        echo "pulling branch $branch wasn't successful";
    fi;
    if test -n "$done"; then
        break;
    fi;
done;

stopNest;

header "checking out the revision $revision";

if test -n "$done"; then
    mtn checkout --db "$cacheDB" -r "$revision" "$out" -b "${branch}"
else
    echo "Needed revision still not found. Exiting";
    exit 1;
fi;

stopNest

header "clearing _MTN in the output"

rm -rf "$out/_MTN"

stopNest