tools: ratbactl.test: if RATBAGCTL_DEVEL is set, use the existing server

When there's a bug that's triggered by the test suite it's hard to figure out
what exactly crashes. So allow starting ratbagd.devel manually and run the
test suite against that process so we can gdb it.

The steps required for this are a bit insane, so the instructions are listed.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

tools/ratbagctl.test.in

@@ -603,9 +603,23 @@ class TestRatbagCtlLED(TestRatbagCtl):
 def setUpModule():
     global ratbagd_process, ratbagd, parser
 
-    ratbagd_process = toolbox.start_ratbagd()
-
-    assert ratbagd_process is not None
+    # if the environment variable is set, we're manually debugging.
+    # To do actually do this:
+    # - copy the org.freedesktop.ratbag_devel1.conf to
+    # /etc/dbus-1/system.d
+    # - start builddir/ratbagd.devel (in gdb if need be)
+    # - set RATBAGCTL_DEVEL to org.freesktop.ratbag_devel1_<8-digit-git-sha>
+    # - run builddir/ratbagctl.test
+    # Note that the .conf will be overwritten if you run the test normally
+    # and you have to re-copy it.
+    # Note that the git sha will obviously change and you have to re-do all
+    # this.
+    #
+    # Yes, this is a bit insane.
+    ratbagd_process = None
+    if not os.environ.get('RATBAGCTL_DEVEL'):
+        ratbagd_process = toolbox.start_ratbagd()
+        assert ratbagd_process is not None
 
     ratbagd = toolbox.open_ratbagd(ratbagd_process)
     assert ratbagd is not None