tests: test that the pid returned by `hg serve` looks reasonable

This failed on windows before win32.spawndetached has been fixed. The process
name was "cmd.exe" and not "hg.exe" or "python.exe".

tests/test-treediscovery.t

@@ -29,6 +29,15 b' Both are empty:'
   $ hg init empty1
   $ hg init empty2
   $ tstart empty2
+check if process of pid looks reasonable ('hg' normally, 'python' for run-tests.py -l)
+#if windows
+ps of mingw does not support -p, tasklist is on any windows machine since XP
+  $ tasklist //NH //fi "pid eq `cat hg.pid`" | grep '  '
+  (.* )?(hg|python)\.exe( .*)? (re)
+#else
+  $ ps --no-heading -p `cat hg.pid`
+  (.* )?(hg|python)( .*)? (re)
+#endif
   $ hg incoming -R empty1 $remote
   comparing with http://localhost:$HGPORT/
   no changes found