blackbox: also log alias expansions

This should be extremely useful for helping users debug without having
to see their complete configuration.

Shell aliases do not get their expansion logged, because we don't look
and see if we're in a repo before we dive into the execution of a
shell alias. As a result, the ui object doesn't know where to log.

mercurial/dispatch.py

@@ -500,6 +500,8 b' class cmdalias(object):'
             ui.debug("alias '%s' shadows command '%s'\n" %
                      (self.name, self.cmdname))
 
+        ui.log('commandalias', "alias '%s' expands to '%s'\n",
+               self.name, self.definition)
         if util.safehasattr(self, 'shell'):
             return self.fn(ui, *args, **opts)
         else:

tests/test-blackbox.t

@@ -4,6 +4,8 b' setup'
   > blackbox=
   > mock=$TESTDIR/mockblackbox.py
   > mq=
+  > [alias]
+  > confuse = log --limit 3
   > EOF
   $ hg init blackboxtest
   $ cd blackboxtest
@@ -17,6 +19,18 b' command, exit codes, and duration'
   1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> add a exited 0 after * seconds (glob)
   1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000+ (5000)> blackbox
 
+alias expansion is logged
+  $ hg confuse
+  $ hg blackbox
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> add a
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> add a exited 0 after * seconds (glob)
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000+ (5000)> blackbox
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000+ (5000)> blackbox --config blackbox.dirty=True exited 0 after * seconds (glob)
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> confuse
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> alias 'confuse' expands to 'log --limit 3'
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> confuse exited 0 after * seconds (glob)
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> blackbox
+
 incoming change tracking
 
 create two heads to verify that we only see one change in the log later