[PATCH 2 of 5] obsolete: drop successors sets which are subset of another one

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at logilab.fr>
# Date 1352509019 -3600
# Node ID 929a4dc33ad3401ced4b099bdbf29d714115d2df
# Parent  c9b7c8ba13c0904afea4ecf035db2c02befab070
obsolete: drop successors sets which are subset of another one

If both "(B,)" and "(B, C)" are successors set of "A", "(B,)" is dropped.
We won't be interrested in detection such divergence scenario.

diff --git a/mercurial/obsolete.py b/mercurial/obsolete.py
--- a/mercurial/obsolete.py
+++ b/mercurial/obsolete.py
@@ -518,7 +518,24 @@
                 # computation was succesful for *all* marker.
                 # Add computed successors set to the cache
                 # (will be poped from to proceeed on the next iteration)
-                cache[node] = list(set(tuple(r) for r in lss if r))
+                #
+                # We remove successors set that are subset of another one
+                # this fil
+                candsucset = sorted(((len(ss), set(ss), ss) for ss in lss),
+                                    reverse=True)
+                finalsucset = []
+                for cl, cs, css in candsucset:
+                    if not css:
+                        # remove empty successors set
+                        continue
+                    for fs, fss in finalsucset:
+                        if cs.issubset(fs):
+                            break
+                    else:
+                        finalsucset.append((cs, css))
+                finalsucset = [s[1] for s in finalsucset]
+                finalsucset.reverse() # put small successors set first
+                cache[node] = finalsucset
     return cache[initialnode]
 
 def _knownrevs(repo, nodes):
diff --git a/tests/test-obsolete-divergent.t b/tests/test-obsolete-divergent.t
--- a/tests/test-obsolete-divergent.t
+++ b/tests/test-obsolete-divergent.t
@@ -75,8 +75,8 @@
   d20a80d4def3
       d20a80d4def3
   007dc284c1f8
+      392fd25390da
       82623d38b9ba
-      392fd25390da
   82623d38b9ba
       82623d38b9ba
   392fd25390da
@@ -139,8 +139,8 @@
   d20a80d4def3
       d20a80d4def3
   007dc284c1f8
+      392fd25390da
       82623d38b9ba
-      392fd25390da
   82623d38b9ba
       82623d38b9ba
   392fd25390da
@@ -396,3 +396,18 @@
 
   $ cd ..
 
+
+Subset does not diverge
+------------------------------
+
+Do not report divergent successors-set if it is a subset of another
+successors-set. (report [A,B] not [A] + [A,B])
+
+  $ newcase subset
+  $ hg debugobsolete `getid A_0` `getid A_2`
+  $ hg debugobsolete `getid A_0` `getid A_1` `getid A_2`
+  $ hg debugsuccessorssets 'desc('A_0')'
+  007dc284c1f8
+      82623d38b9ba 392fd25390da
+
+  $ cd ..