[PATCH 7 of 9 V2] obsolete: compute extinct changesets

[pierre-yves.david at logilab.fr]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at ens-lyon.org>
# Date 1341596049 -7200
# Node ID 6c0a3b9bcb4c319714a0edd07ee99dea4487f3c4
# Parent  4c9a282e873277ae9d225505bc28a8822da4253f
obsolete: compute extinct changesets

`extinct` changesets are obsolete changesets with obsolete descendants only. They
are of no interest anymore and can be:

- exclude from exchange
- hidden to the user in most situation
- safely garbage collected

This changeset just allows mercurial to detect them.

The implementation is a bit naive, as for unstable changesets. We better use a
simple revset query and a cache, but simple version comes first.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -233,10 +233,25 @@ class changectx(object):
     def obsolete(self):
         """True if the changeset is obsolete"""
         return (self.node() in self._repo.obsstore.precursors
                 and self.phase() > phases.public)
 
+    def extinct(self):
+        """True if the changeset is extinct"""
+        # We should just compute a cache a check againts it.
+        # see revset implementation for details
+        #
+        # But this naive implementation does not require cache
+        if self.phase() <= phases.public:
+            return False
+        if not self.obsolete():
+            return False
+        for desc in self.descendants():
+            if not desc.obsolete():
+                return False
+        return True
+
     def unstable(self):
         """True if the changeset is not obsolete but it's ancestor are"""
         # We should just compute /(obsolete()::) - obsolete()/
         # and keep it in a cache.
         #
diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -566,10 +566,17 @@ def draft(repo, subset, x):
     Changeset in draft phase."""
     getargs(x, 0, 0, _("draft takes no arguments"))
     pc = repo._phasecache
     return [r for r in subset if pc.phase(repo, r) == phases.draft]
 
+def extinct(repo, subset, x):
+    """``extinct()``
+    obsolete changeset with obsolete descendant only."""
+    getargs(x, 0, 0, _("obsolete takes no arguments"))
+    extinctset = set(repo.revs('(obsolete()::) - (::(not obsolete()))'))
+    return [r for r in subset if r in extinctset]
+
 def extra(repo, subset, x):
     """``extra(label, [value])``
     Changesets with the given label in the extra metadata, with the given
     optional value.
 
@@ -1363,10 +1370,11 @@ symbols = {
     "date": date,
     "desc": desc,
     "descendants": descendants,
     "_firstdescendants": _firstdescendants,
     "draft": draft,
+    "extinct": extinct,
     "extra": extra,
     "file": hasfile,
     "filelog": filelog,
     "first": first,
     "follow": follow,
diff --git a/tests/test-obsolete.t b/tests/test-obsolete.t
--- a/tests/test-obsolete.t
+++ b/tests/test-obsolete.t
@@ -298,5 +298,15 @@ detect outgoing obsolete and unstable
   $ hg push ../tmpc/
   pushing to ../tmpc/
   searching for changes
   abort: push includes an unstable changeset: 7878242aeece!
   [255]
+
+Test that extinct changeset are properly detected
+
+  $ hg log -r 'extinct()'
+  changeset:   3:cdbce2fbb163
+  parent:      1:7c3bad9141dc
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     add new_c
+