reabase: call rewriteutil.precheck() a bit later

We now filter out descendants of divergence-causing commits in
`_handleskippingobsolete()`. The filtered-out commits are removed from
the rebase set (`destmap` and `state`). We should therefore call
`rewriteutil.precheck()` after `_handleskippingobsolete()`. This patch
does that. It hasn't mattered so far because `rewriteutil.precheck()`
doesn't yet check for divergence, but it will soon.

This affects one test where we now fail because the user is trying to
rebase an ancestor instead of failing because they tried to rebase a
public commit. We have several similar tests just after, where we
still fail because of the phase, so that seems fine. The difference in
behavior also seems fine to me.

Differential Revision: https://phab.mercurial-scm.org/D10258

hgext/rebase.py

@@ -413,15 +413,6 b' class rebaseruntime(object):'
         if not destmap:
             return _nothingtorebase()
 
-        rebaseset = destmap.keys()
-        if not self.keepf:
-            try:
-                rewriteutil.precheck(self.repo, rebaseset, action=b'rebase')
-            except error.Abort as e:
-                if e.hint is None:
-                    e.hint = _(b'use --keep to keep original changesets')
-                raise e
-
         result = buildstate(self.repo, destmap, self.collapsef)
 
         if not result:
@@ -450,6 +441,15 b' class rebaseruntime(object):'
         # Calculate self.obsolete_* sets
         self._handleskippingobsolete()
 
+        rebaseset = destmap.keys()
+        if not self.keepf:
+            try:
+                rewriteutil.precheck(self.repo, rebaseset, action=b'rebase')
+            except error.Abort as e:
+                if e.hint is None:
+                    e.hint = _(b'use --keep to keep original changesets')
+                raise e
+
         self.prepared = True
 
     def _assignworkingcopy(self):

tests/test-rebase-scenario-global.t

@@ -325,9 +325,8 b' Check rebasing public changeset'
 
   $ hg pull --config phases.publish=True -q -r 6 . # update phase of 6
   $ hg rebase -d 0 -b 6
-  abort: cannot rebase public changesets
-  (see 'hg help phases' for details)
-  [10]
+  nothing to rebase
+  [1]
   $ hg rebase -d 5 -b 6
   abort: cannot rebase public changesets
   (see 'hg help phases' for details)