obsolete: reports the number of local changeset obsoleted when unbundling This is a first basic visible usage of the changes tracking in the transaction. We adds a new function computing the pre-existing changesets obsoleted by a transaction and a transaction call back displaying this information. Example output: added 1 changesets with 1 changes to 1 files (+1 heads) 3 new obsolescence markers obsoleted 1 changesets The goal is to evolve the transaction summary into something bigger, gathering existing output there and adding new useful one. This patch is a good first step on this road. The new output is basic but give a user to the content of tr.changes['obsmarkers'] and give an idea of the new options we haves. I expect to revisit the message soon. The caller recording the transaction summary should also be moved into a more generic location but further refactoring is needed before it can happen.

--- a/tests/test-bookmarks-pushpull.t	Tue Jun 27 02:45:09 2017 +0200
+++ b/tests/test-bookmarks-pushpull.t	Wed Jun 28 03:54:19 2017 +0200
@@ -484,6 +484,7 @@
   remote: adding file changes
   remote: added 2 changesets with 2 changes to 1 files (+1 heads)
   remote: 2 new obsolescence markers
+  remote: obsoleted 1 changesets
   updating bookmark Y
   $ hg -R ../a book
      @                         1:0d2164f0ce0d