[PATCH 1 of 6 V2] hidden: add a function returning ancestors of revs within a domain

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at octobus.net>
# Date 1495372906 -7200
#      Sun May 21 15:21:46 2017 +0200
# Node ID 5f964af88a0fae242ce24b0478c676d2056e0dc6
# Parent  8db2feb04cebc1878c6232dd2650f2c5468d350e
# EXP-Topic fast-compute-hidden
# Available At https://www.mercurial-scm.org/repo/users/marmoute/mercurial/
#              hg pull https://www.mercurial-scm.org/repo/users/marmoute/mercurial/ -r 5f964af88a0f
hidden: add a function returning ancestors of revs within a domain

See documentation for details. This will be used to improve the hidden
computation algorithm. See new changesets for usage.

diff --git a/mercurial/repoview.py b/mercurial/repoview.py
--- a/mercurial/repoview.py
+++ b/mercurial/repoview.py
@@ -92,6 +92,31 @@ def _getstatichidden(repo):
                     heappush(heap, -parent)
     return hidden
 
+def _domainancestors(pfunc, revs, domain):
+    """return ancestors of 'revs' within 'domain'
+
+    - pfunc(r): a funtion returning parent of 'r',
+    - revs: iterable of revnum,
+    - domain: consistent set of revnum.
+
+    The domain must be consistent: no connected subset are the ancestors of
+    another connected subset. In other words, if the parents of a revision are
+    not in the domains, no other ancestors of that revision.
+
+    (Ancestors are returned inclusively, 'revs' must be within the domain or
+    direct children of it.)
+    """
+    stack = list(revs)
+    ancs = set(stack)
+    while stack:
+        for p in pfunc(stack.pop()):
+            nbanc = len(ancs)
+            if p != nullrev and p in domain:
+                ancs.add(p)
+            if nbanc != len(ancs): # avoid double membership testing
+                stack.append(p)
+    return ancs
+
 cacheversion = 1
 cachefile = 'cache/hidden'