amend: preserve phase of amended revision (issue3602)

New commit from the amend process were created without any phase contraint. If
the amended changeset had a different phase from it's parent, the phases data
were lost.

The changeset ensure the new commit are created in the same phase than the
original changeset.

mercurial/cmdutil.py

@@ -10,7 +10,7 b' from i18n import _'
 import os, sys, errno, re, tempfile
 import util, scmutil, templater, patch, error, templatekw, revlog, copies
 import match as matchmod
-import subrepo, context, repair, bookmarks, graphmod, revset
+import subrepo, context, repair, bookmarks, graphmod, revset, phases
 
 def parsealiases(cmd):
     return cmd.lstrip("^").split("|")
@@ -1668,7 +1668,12 b' def amend(ui, repo, commitfunc, old, ext'
                              user=user,
                              date=date,
                              extra=extra)
+        ph = repo.ui.config('phases', 'new-commit', phases.draft)
+        try:
+            repo.ui.setconfig('phases', 'new-commit', old.phase())
         newid = repo.commitctx(new)
+        finally:
+            repo.ui.setconfig('phases', 'new-commit', ph)
         if newid != old.node():
             # Reroute the working copy parent to the new changeset
             repo.setparents(newid, nullid)

tests/test-commit-amend.t

@@ -355,3 +355,18 b" first graft something so there's an addi"
   $ hg log -r . --debug | grep extra
   extra:       branch=a
   extra:       source=2647734878ef0236dda712fae9c1651cf694ea8a
+
+Preserve phase
+
+  $ hg phase '.^::.'
+  11: draft
+  13: draft
+  $ hg phase --secret --force .
+  $ hg phase '.^::.'
+  11: draft
+  13: secret
+  $ hg commit --amend -m 'amend for phase' -q
+  $ hg phase '.^::.'
+  11: draft
+  13: secret
+