setdiscovery: improves logged message

The 'srvheads' list contains all server heads including the common ones. We
adjust 'ui.log' message to provide more useful information about server heads
locally unknown. The performance impact of turning the list to set is
negligible (about 1e-4s) compared to the rest of the discovery cost, so I'm
taking the easy path.

mercurial/setdiscovery.py

@@ -241,8 +241,10 b' def findcommonheads(ui, local, remote,'
     elapsed = util.timer() - start
     ui.progress(_('searching'), None)
     ui.debug("%d total queries in %.4fs\n" % (roundtrips, elapsed))
-    msg = 'found %d common and %d missing heads, %d roundtrips in %.4fs\n'
-    ui.log('discovery', msg, len(result), len(srvheadhashes), roundtrips,
+    msg = ('found %d common and %d unknown server heads,'
+           ' %d roundtrips in %.4fs\n')
+    missing = set(result) - set(srvheads)
+    ui.log('discovery', msg, len(result), len(missing), roundtrips,
            elapsed)
 
     if not result and srvheadhashes != [nullid]:

tests/test-setdiscovery.t

@@ -404,7 +404,7 b' fixed in 86c35b7ae300:'
   101 102 103 104 105 106 107 108 109 110  (no-eol)
   $ hg -R r1 --config extensions.blackbox= blackbox
   * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> outgoing r2 *-T{rev} * (glob)
-  * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> found 101 common and 101 missing heads, 2 roundtrips in *.????s (glob)
+  * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> found 101 common and 1 unknown server heads, 2 roundtrips in *.????s (glob)
   * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> -R r1 outgoing r2 *-T{rev} * --config *extensions.blackbox=* exited 0 after *.?? seconds (glob)
   * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> blackbox (glob)
   $ cd ..