histedit: reword message when a changeset produces no changes

There are various ways to use histedit such that an item in
the list of things to perform will not result in a change
relative to the previous repository state.

When that happens, histedit does not keep the commit/message.

This changes the note to try to explain to the user that it
will not be present in their history.

hgext/histedit.py

@@ -482,7 +482,7 b' class histeditaction(object):'
         rulectx."""
         ctx = self.repo['.']
         if ctx.node() == self.state.parentctxnode:
-            self.repo.ui.warn(_('%s: empty changeset\n') %
+            self.repo.ui.warn(_('%s: skipping changeset (no changes)\n') %
                               node.short(self.node))
             return ctx, [(self.node, tuple())]
         if ctx.node() == self.node:

tests/test-histedit-fold-non-commute.t

@@ -117,12 +117,14 b' fix up'
   (hg histedit --continue to resume)
 
 just continue this time
+keep the non-commuting change, and thus the pending change will be dropped
   $ hg revert -r 'p1()' e
   $ hg resolve --mark e
   (no more unresolved files)
   continue: hg histedit --continue
+  $ hg diff
   $ hg histedit --continue 2>&1 | fixbundle
-  7b4e2f4b7bcd: empty changeset
+  7b4e2f4b7bcd: skipping changeset (no changes)
 
 log after edit
   $ hg log --graph
@@ -262,7 +264,7 b' just continue this time'
   (no more unresolved files)
   continue: hg histedit --continue
   $ hg histedit --continue 2>&1 | fixbundle
-  7b4e2f4b7bcd: empty changeset
+  7b4e2f4b7bcd: skipping changeset (no changes)
 
 log after edit
   $ hg log --graph

tests/test-histedit-non-commute.t

@@ -171,7 +171,7 b' just continue this time'
   (no more unresolved files)
   continue: hg histedit --continue
   $ hg histedit --continue 2>&1 | fixbundle
-  7b4e2f4b7bcd: empty changeset
+  7b4e2f4b7bcd: skipping changeset (no changes)
 
 log after edit
   $ hg log --graph
@@ -254,7 +254,7 b' second edit also fails, but just continu'
   (no more unresolved files)
   continue: hg histedit --continue
   $ hg histedit --continue 2>&1 | fixbundle
-  7b4e2f4b7bcd: empty changeset
+  7b4e2f4b7bcd: skipping changeset (no changes)
 
 post message fix
   $ hg log --graph