phases: add a 'registernew' method to set new phases

This new function will be used by code that adds new changesets. It ajusts the
phase boundary to make sure added changesets are at least in their target
phase (they end up in an higher phase if their parents are in a higher phase).

Having a dedicated function also simplify the phases tracking. All the new
nodes are passed as argument, so we know that all of them needs to have their
new phase registered. We also know that no other nodes will be affected, so no
extra computation are needed.

This function differ from 'retractboundary' where some nodes might change
phase while some other might not. It can also affect nodes not passed as
parameters.

These simplification also apply to the computation itself. For now we use
'_retractboundary' there by convenience, but we may introduces simpler code
later.

While registering new revisions, we still need to check the actual phases of
the added node because it might be higher than the target phase (eg: target is
draft but parent is secret).

We will migrate users over the next changesets.

mercurial/phases.py

@@ -294,6 +294,19 b' class phasecache(object):'
         tr.addfilegenerator('phase', ('phaseroots',), self._write)
         tr.hookargs['phases_moved'] = '1'
 
+    def registernew(self, repo, tr, targetphase, nodes):
+        repo = repo.unfiltered()
+        self._retractboundary(repo, tr, targetphase, nodes)
+        if tr is not None and 'phases' in tr.changes:
+            phasetracking = tr.changes['phases']
+            torev = repo.changelog.rev
+            phase = self.phase
+            for n in nodes:
+                rev = torev(n)
+                revphase = phase(repo, rev)
+                _trackphasechange(phasetracking, rev, None, revphase)
+        repo.invalidatevolatilesets()
+
     def advanceboundary(self, repo, tr, targetphase, nodes):
         """Set all 'nodes' to phase 'targetphase'
 
@@ -417,6 +430,16 b' def retractboundary(repo, tr, targetphas'
     phcache.retractboundary(repo, tr, targetphase, nodes)
     repo._phasecache.replace(phcache)
 
+def registernew(repo, tr, targetphase, nodes):
+    """register a new revision and its phase
+
+    Code adding revisions to the repository should use this function to
+    set new changeset in their target phase (or higher).
+    """
+    phcache = repo._phasecache.copy()
+    phcache.registernew(repo, tr, targetphase, nodes)
+    repo._phasecache.replace(phcache)
+
 def listphases(repo):
     """List phases root for serialization over pushkey"""
     # Use ordered dictionary so behavior is deterministic.