diff mercurial/graphmod.py @ 32921:27932a76a88d

dagop: split module hosting DAG-related algorithms from revset

This module hosts the following functions. They are somewhat similar (e.g.
scanning revisions using heap queue or stack) and seem non-trivial in
algorithmic point of view.

 - _revancestors()
 - _revdescendants()
 - reachableroots()
 - _toposort()

I was thinking of adding revset._fileancestors() generator for better follow()
implementation, but it would be called from context.py as well. So I decided
to create new module.

Naming is hard. I couldn't come up with any better module name, so it's called
"dag operation" now. I rejected the following candidates:

 - ancestor.py - existing, revlog-level DAG algorithm
 - ancestorset.py - doesn't always return a set
 - dagalgorithm.py - hard to type
 - dagutil.py - existing
 - revancestor.py - I want to add fileancestors()

  % wc -l mercurial/dagop.py mercurial/revset.py
    339 mercurial/dagop.py
   2020 mercurial/revset.py
   2359 total

--- a/mercurial/graphmod.py	Thu Jun 15 17:14:53 2017 -0700
+++ b/mercurial/graphmod.py	Sun Oct 16 18:03:24 2016 +0900
@@ -21,7 +21,7 @@
 
 from .node import nullrev
 from . import (
-    revset,
+    dagop,
     smartset,
     util,
 )
@@ -70,7 +70,7 @@
                 # through all revs (issue4782)
                 if not isinstance(revs, smartset.baseset):
                     revs = smartset.baseset(revs)
-                gp = gpcache[mpar] = sorted(set(revset.reachableroots(
+                gp = gpcache[mpar] = sorted(set(dagop.reachableroots(
                     repo, revs, [mpar])))
             if not gp:
                 parents.append((MISSINGPARENT, mpar))