{ nixpkgs ? ../nixpkgs

{ nixpkgs ? /etc/nixos/nixpkgs

sub scmPath {
    return getHydraPath . "/scm" ;
}

    # First figure out the last-modified revision of the URI.

    my $clonePath;
    mkpath(scmPath);
    $clonePath = scmPath . "/" . sha256_hex($uri);    

    if (! -d $clonePath) {
        (my $res, $stdout, $stderr) = captureStdoutStderr(600,
            ("git", "clone", $uri, $clonePath));
        die "Error cloning git repo at `$uri':\n$stderr" unless $res;
    }
    # git pull + check rev
    chdir $clonePath or die $!;

        ("git", "ls-remote", $uri, "refs/heads/".$branch));
    die "Cannot get head revision of Git branch '$branch' at `$uri':\n$stderr" unless $res;

        ("git", "pull"));
    die "Error pulling latest change git repo at `$uri':\n$stderr" unless $res;
    (my $res1, $stdout, $stderr) = captureStdoutStderr(600,
        ("git", "ls-remote", $clonePath, "refs/heads/".$branch));
    die "Cannot get head revision of Git branch '$branch' at `$uri':\n$stderr" unless $res1;

    if (! defined $cachedInput ) {
        ($cachedInput) = $db->resultset('CachedGitInputs')->search(
            {uri => $uri, branch => $branch, lastseen => {">", $timestamp - 3600}},
            {rows => 1, order_by => "lastseen DESC"});
    }

        $timestamp = $cachedInput->timestamp;

        ($cachedInput) = $db->resultset('CachedGitInputs')->search(
            {uri => $uri, branch => $branch, sha256hash => $sha256});

        if (!defined $cachedInput) {
            txn_do($db, sub {
                $db->resultset('CachedGitInputs')->update_or_create(
                    { uri => $uri
                    , branch => $branch
                    , revision => $revision
                    , timestamp => $timestamp
                    , lastseen => $timestamp
                    , sha256hash => $sha256
                    , storepath => $storePath
                    });

        txn_do($db, sub {
            $db->resultset('CachedGitInputs')->update_or_create(
                { uri => $uri
                , branch => $branch
                , revision => $revision
                , sha256hash => $sha256
                , storepath => $storePath

        } else {
            $timestamp = $cachedInput->timestamp;
            txn_do($db, sub {
                $cachedInput->update({lastseen => time});

        }

sub scmPath {
    return getHydraPath . "/scm" ;
}

    die "Error getting head of $branch from `$uri':\n$stderr" unless $res;

    die "Error getting head of $branch from `$uri':\n$stderr" unless $res1;

    timestamp     integer not null, -- when we first saw this hash
    lastSeen      integer not null, -- when we last saw this hash