Approaching the exclusive “sub-minute” build time club

For the first time in at least two years (and probably even longer), debhelper with the 10.6.2 upload broke the 1 minute milestone for build time (by mere 2 seconds – look for “Build needed 00:00:58, […]”).  Sadly, the result it is not deterministic and the 10.6.3 upload needed 1m + 5s to complete on the buildds.

This is not the result of any optimizations I have done in debhelper itself.  Instead, it is the result of “questionable use of developer time” for the sake of meeting an arbitrary milestone. Basically, I made it possible to parallelize more of the debhelper build (10.6.1) and finally made it possible to run the tests in parallel (10.6.2).

In 10.6.2, I also made the most of the tests run against all relevant compat levels.  Previously, it would only run the tests against one compat level (either the current one or a hard-coded older version).

Testing more than one compat turned out to be fairly simple given a proper test library (I wrote a “Test::DH” module for the occasion).  Below is an example, which is the new test case that I wrote for Debian bug #866570.

$ cat t/dh_install/03-866570-dont-install-from-host.t
#!/usr/bin/perl
use strict;
use warnings;
use Test::More;

use File::Basename qw(dirname);
use lib dirname(dirname(__FILE__));
use Test::DH;
use File::Path qw(remove_tree make_path);
use Debian::Debhelper::Dh_Lib qw(!dirname);

plan(tests => 1);

each_compat_subtest {
  my ($compat) = @_;
  # #866570 - leading slashes must *not* pull things from the root FS.
  make_path('bin');
  create_empty_file('bin/grep-i-licious');
  ok(run_dh_tool('dh_install', '/bin/grep*'));
  ok(-e "debian/debhelper/bin/grep-i-licious", "#866570 [${compat}]");
  ok(!-e "debian/debhelper/bin/grep", "#866570 [${compat}]");
  remove_tree('debian/debhelper', 'debian/tmp');
};

I have cheated a bit on the implementation; while the test runs in a temporary directory, the directory is reused between compat levels (accordingly, there is a “clean up” step at the end of the test).

If you want debhelper to maintain this exclusive (and somewhat arbitrary) property (deterministically), you are more than welcome to help me improve the Makefile.   I am not sure I can squeeze any more out of it with my (lack of) GNU make skills.