revset: refactor the non-public phase code

Code for draft and secret are the same. We'll make it more complex to
take advantages of the set recomputed in C, so we first refactor the
code to only have one place to update (and make sure all behave
properly).

We do not refactor the 'public()' code because it does not have a natively
computed set.

mercurial/revset.py

@@ -803,16 +803,6 b' def divergent(repo, subset, x):'
     divergent = obsmod.getrevs(repo, 'divergent')
     return subset & divergent
 
-def draft(repo, subset, x):
-    """``draft()``
-    Changeset in draft phase."""
-    # i18n: "draft" is a keyword
-    getargs(x, 0, 0, _("draft takes no arguments"))
-    phase = repo._phasecache.phase
-    target = phases.draft
-    condition = lambda r: phase(repo, r) == target
-    return subset.filter(condition, cache=False)
-
 def extinct(repo, subset, x):
     """``extinct()``
     Obsolete changesets with obsolete descendants only.
@@ -1472,6 +1462,28 b' def parents(repo, subset, x):'
     ps -= set([node.nullrev])
     return subset & ps
 
+def _phase(repo, subset, target):
+    """helper to select all rev in phase <target>"""
+    phase = repo._phasecache.phase
+    condition = lambda r: phase(repo, r) == target
+    return subset.filter(condition, cache=False)
+
+def draft(repo, subset, x):
+    """``draft()``
+    Changeset in draft phase."""
+    # i18n: "draft" is a keyword
+    getargs(x, 0, 0, _("draft takes no arguments"))
+    target = phases.draft
+    return _phase(repo, subset, target)
+
+def secret(repo, subset, x):
+    """``secret()``
+    Changeset in secret phase."""
+    # i18n: "secret" is a keyword
+    getargs(x, 0, 0, _("secret takes no arguments"))
+    target = phases.secret
+    return _phase(repo, subset, target)
+
 def parentspec(repo, subset, x, n):
     """``set^0``
     The set.
@@ -1730,16 +1742,6 b' def roots(repo, subset, x):'
     cs = _children(repo, subset, s)
     return subset - cs
 
-def secret(repo, subset, x):
-    """``secret()``
-    Changeset in secret phase."""
-    # i18n: "secret" is a keyword
-    getargs(x, 0, 0, _("secret takes no arguments"))
-    phase = repo._phasecache.phase
-    target = phases.secret
-    condition = lambda r: phase(repo, r) == target
-    return subset.filter(condition, cache=False)
-
 def sort(repo, subset, x):
     """``sort(set[, [-]key...])``
     Sort set by keys. The default sort order is ascending, specify a key