rebase: extract function for rebasing a single node

We currently have _performrebase() and _performrebasesubset(), but we
don't have a method for rebasing a single node (that's inside a loop
in _performrebasesubset()). I think it makes sense to have such a
method, so that's what this patch does. I think it may simplify future
patches I'm working on that have to do with transactions, but I think
this patch makes sense on its own whether or not that future work
happens.

Differential Revision: https://phab.mercurial-scm.org/D2809

hgext/rebase.py

@@ -430,17 +430,27 b' class rebaseruntime(object):'
         ui.note(_('rebase merging completed\n'))
 
     def _performrebasesubset(self, tr, subset, pos, total):
-        repo, ui, opts = self.repo, self.ui, self.opts
-        sortedrevs = repo.revs('sort(%ld, -topo)', subset)
+        sortedrevs = self.repo.revs('sort(%ld, -topo)', subset)
         allowdivergence = self.ui.configbool(
             'experimental', 'evolution.allowdivergence')
         if not allowdivergence:
-            sortedrevs -= repo.revs(
+            sortedrevs -= self.repo.revs(
                 'descendants(%ld) and not %ld',
                 self.obsoletewithoutsuccessorindestination,
                 self.obsoletewithoutsuccessorindestination,
             )
+        posholder = [pos]
+        def progress(ctx):
+            posholder[0] += 1
+            self.repo.ui.progress(_("rebasing"), posholder[0],
+                                  ("%d:%s" % (ctx.rev(), ctx)), _('changesets'),
+                                  total)
         for rev in sortedrevs:
+            self._rebasenode(tr, rev, allowdivergence, progress)
+        return posholder[0]
+
+    def _rebasenode(self, tr, rev, allowdivergence, progressfn):
+        repo, ui, opts = self.repo, self.ui, self.opts
             dest = self.destmap[rev]
             ctx = repo[rev]
             desc = _ctxdesc(ctx)
@@ -470,10 +480,8 b' class rebaseruntime(object):'
                                       self.skipped))
                 self.state[rev] = dest
             elif self.state[rev] == revtodo:
-                pos += 1
                 ui.status(_('rebasing %s\n') % desc)
-                ui.progress(_("rebasing"), pos, ("%d:%s" % (rev, ctx)),
-                            _('changesets'), total)
+            progressfn(ctx)
                 p1, p2, base = defineparents(repo, rev, self.destmap,
                                              self.state, self.skipped,
                                              self.obsoletenotrebased)
@@ -538,7 +546,6 b' class rebaseruntime(object):'
             else:
                 ui.status(_('already rebased %s as %s\n') %
                           (desc, repo[self.state[rev]]))
-        return pos
 
     def _finishrebase(self):
         repo, ui, opts = self.repo, self.ui, self.opts