Bug#768456: Version 3 including ansgar's and pitti's feedback

[Didier Roche]

Here is the v3 of the patch, which includes ansgar's and pitti's 
feedback. Thanks to them!

The only suggestion I couldn't integrate is Martin's system vs exec one. 
I had to change keep it as system() call as we are evaluating one unit 
after another as the scripts can accepts multiple units, and so exec 
would prefer the evaluation and inclusion of other units passed as 
parameters.
Does this make sense? The downside is that we loose the return code, 
indeed (we could concatenate it if needed).

Cheers,
Didier
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diff -Nru init-system-helpers-1.21/debian/changelog init-system-helpers-1.22/debian/changelog
--- init-system-helpers-1.21/debian/changelog	2014-08-21 07:40:58.000000000 +0200
+++ init-system-helpers-1.22/debian/changelog	2014-11-07 15:13:08.000000000 +0100
@@ -1,3 +1,16 @@
+init-system-helpers (1.22) UNRELEASED; urgency=medium
+
+  * deb-system-invoke: don't start disabled systemd services (in case
+    of systemd only services), when there is no init script.
+    Add some conditions to start the job on deb-system-invoke [restart|start],
+    during package upgrade: (Closes: #768456)
+    - deb-system-invoke start <unit> don't do anything on systemd if the
+      service is disabled.
+    - deb-system-invoke restart <unit> only restart a disabled service if
+      if the daemon was already running (forced by the admin).
+
+ -- Didier Roche <didrocks at ubuntu.com>  Fri, 07 Nov 2014 15:01:27 +0100
+
 init-system-helpers (1.21) unstable; urgency=medium
 
   * Demote augeas-tools to Suggests and let the systemd2init tool error out
diff -Nru init-system-helpers-1.21/script/deb-systemd-invoke init-system-helpers-1.22/script/deb-systemd-invoke
--- init-system-helpers-1.21/script/deb-systemd-invoke	2014-08-21 07:40:58.000000000 +0200
+++ init-system-helpers-1.22/script/deb-systemd-invoke	2014-11-07 17:08:10.000000000 +0100
@@ -77,4 +77,24 @@
     }
 }
 
-exec '/bin/systemctl', @ARGV;
+# If the job is disabled and is not currently running, the job is not started or restarted.
+# However, if the job is disabled but has been forced into the running state, we *do* stop
+# and restart it since this is expected behaviour for the admin who forced the start.
+if ($action eq "start" || $action eq "restart") {
+    for my $unit (@units) {
+        system('/bin/systemctl', '--quiet', 'is-enabled', '--', $unit);
+        my $unit_enabled = $?>>8 == 0 ? 1 : 0;
+        system('/bin/systemctl', '--quiet', 'is-active', '--', $unit);
+        my $unit_active = $?>>8 == 0 ? 1 : 0;
+        if (!$unit_enabled && $action eq "start") {
+            print STDERR "$unit is disabled, not starting it.\n";
+        } elsif (!$unit_enabled && !$unit_active && $action eq "restart") {
+            print STDERR "$unit is disabled and not running, not starting it.\n";
+        }
+        else {
+            system('/bin/systemctl', "$action", "$unit");
+        }
+    }
+} else {
+    exec '/bin/systemctl', @ARGV;
+}