[PATCH 2 of 7] revlog: deltachain() returns chain of revs need to construct a revision

[in3xes at gmail.com]

# HG changeset patch
# User Pradeepkumar Gayam <in3xes at gmail.com>
# Date 1281076831 -19800
# Node ID 0155341e71903631a6e91b2cf237ac000529161d
# Parent  ea75c464fe41b33161561c131946a47fb94612dc
revlog: deltachain() returns chain of revs need to construct a revision

diff -r ea75c464fe41 -r 0155341e7190 mercurial/revlog.py
--- a/mercurial/revlog.py	Fri Aug 06 12:09:30 2010 +0530
+++ b/mercurial/revlog.py	Fri Aug 06 12:10:31 2010 +0530
@@ -1014,6 +1014,25 @@
     def _chunkclear(self):
         self._chunkcache = (0, '')
 
+    def deltaparent(self, rev):
+        """return previous revision or parentrev according to flags"""
+        if self.base(rev) == rev:
+            return nullrev
+        elif self.flags(rev) & REVIDX_PARENTDELTA:
+            return self.parentrevs(rev)[0]
+        else:
+            return rev-1
+
+
+    def deltachain(self, rev):
+        """return chain of revisions to construct a given revision"""
+        chain = []
+        while self.base(rev) != rev:
+            chain.append(rev)
+            rev = self.deltaparent(rev)
+        chain.reverse()
+        return rev, chain
+
     def revdiff(self, rev1, rev2):
         """return or calculate a delta between two revisions"""
         if rev1 + 1 == rev2 and self.base(rev1) == self.base(rev2):