tracing: trace command function execution

Differential Revision: https://phab.mercurial-scm.org/D4514

mercurial/dispatch.py

@@ -992,6 +992,7 b' def _dispatch(req):'
 def _runcommand(ui, options, cmd, cmdfunc):
     """Run a command function, possibly with profiling enabled."""
     try:
+        with tracing.log("Running %s command" % cmd):
         return cmdfunc()
     except error.SignatureError:
         raise error.CommandError(cmd, _('invalid arguments'))