diff -r cf694e6422f0 -r 67a3204c83c1 tests/testlib/ext-phase-report.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/testlib/ext-phase-report.py	Wed Jul 12 22:39:48 2017 +0200
@@ -0,0 +1,22 @@
+# tiny extension to report phase changes during transaction
+
+from __future__ import absolute_import
+
+def reposetup(ui, repo):
+
+    def reportphasemove(tr):
+        for rev, move in sorted(tr.changes['phases'].iteritems()):
+            if move[0] is None:
+                ui.write(('test-debug-phase: new rev %d:  x -> %d\n'
+                          % (rev, move[1])))
+            else:
+                ui.write(('test-debug-phase: move rev %d: %s -> %d\n'
+                          % (rev, move[0], move[1])))
+
+    class reportphaserepo(repo.__class__):
+        def transaction(self, *args, **kwargs):
+            tr = super(reportphaserepo, self).transaction(*args, **kwargs)
+            tr.addpostclose('report-phase', reportphasemove)
+            return tr
+
+    repo.__class__ = reportphaserepo