amend: mark commit obsolete after moving working copy

We were doing it this way:

  1. move working copy (repo.setparents)
  2. add obsmarkers (scmutil.cleanupnodes)
  3. fix dirstate (dirstate.normal/drop)

Step 1 and 3 are closely related, so let's move them together. It
seems safest to create the obsmarkers last. This patch thus makes the
order 1, 3, 2.

Differential Revision: https://phab.mercurial-scm.org/D10197

mercurial/cmdutil.py

@@ -2967,20 +2967,6 b' def amend(ui, repo, old, extra, pats, op'
 
         # Reroute the working copy parent to the new changeset
         repo.setparents(newid, nullid)
-        mapping = {old.node(): (newid,)}
-        obsmetadata = None
-        if opts.get(b'note'):
-            obsmetadata = {b'note': encoding.fromlocal(opts[b'note'])}
-        backup = ui.configbool(b'rewrite', b'backup-bundle')
-        scmutil.cleanupnodes(
-            repo,
-            mapping,
-            b'amend',
-            metadata=obsmetadata,
-            fixphase=True,
-            targetphase=commitphase,
-            backup=backup,
-        )
 
         # Fixing the dirstate because localrepo.commitctx does not update
         # it. This is rather convenient because we did not need to update
@@ -3003,6 +2989,21 b' def amend(ui, repo, old, extra, pats, op'
         for f in removedfiles:
             dirstate.drop(f)
 
+        mapping = {old.node(): (newid,)}
+        obsmetadata = None
+        if opts.get(b'note'):
+            obsmetadata = {b'note': encoding.fromlocal(opts[b'note'])}
+        backup = ui.configbool(b'rewrite', b'backup-bundle')
+        scmutil.cleanupnodes(
+            repo,
+            mapping,
+            b'amend',
+            metadata=obsmetadata,
+            fixphase=True,
+            targetphase=commitphase,
+            backup=backup,
+        )
+
     return newid