phases: use a more generic way to trigger a phases computation for perf

Querying the tip most revision will require the cache to warm the same as
calling the dedicated method. This avoid using a method that is mostly meant for
internal use and will be renamed in a coming changesets.

contrib/perf.py

@@ -1719,6 +1719,7 b' def perfphases(ui, repo, **opts):'
     timer, fm = gettimer(ui, opts)
     _phases = repo._phasecache
     full = opts.get(b'full')
+    tip_rev = repo.changelog.tiprev()
 
     def d():
         phases = _phases
@@ -1726,7 +1727,7 b' def perfphases(ui, repo, **opts):'
             clearfilecache(repo, b'_phasecache')
             phases = repo._phasecache
         phases.invalidate()
-        phases.loadphaserevs(repo)
+        phases.phase(repo, tip_rev)
 
     timer(d)
     fm.end()

tests/test-contrib-perf.t

@@ -293,6 +293,7 b' perfstatus'
   $ hg perfwalk
   $ hg perfparents
   $ hg perfdiscovery -q .
+  $ hg perf::phases
 
 Test run control
 ----------------