revlog: remove support for parentdelta

We will introduce a more powerful and general delta concept instead,
called generaldelta.

mercurial/localrepo.py

@@ -21,7 +21,7 b' propertycache = util.propertycache'
 class localrepository(repo.repository):
     capabilities = set(('lookup', 'changegroupsubset', 'branchmap', 'pushkey',
                         'known', 'getbundle'))
-    supportedformats = set(('revlogv1', 'parentdelta'))
+    supportedformats = set(('revlogv1',))
     supported = supportedformats | set(('store', 'fncache', 'shared',
                                         'dotencode'))
 
@@ -61,8 +61,6 b' class localrepository(repo.repository):'
                         '\0\0\0\2' # represents revlogv2
                         ' dummy changelog to prevent using the old repo layout'
                     )
-                if self.ui.configbool('format', 'parentdelta', False):
-                    requirements.append("parentdelta")
             else:
                 raise error.RepoError(_("repository %s not found") % path)
         elif create:
@@ -117,8 +115,6 b' class localrepository(repo.repository):'
     def _applyrequirements(self, requirements):
         self.requirements = requirements
         self.sopener.options = {}
-        if 'parentdelta' in requirements:
-            self.sopener.options['parentdelta'] = 1
 
     def _writerequirements(self):
         reqfile = self.opener("requires", "w")

mercurial/revlog.py

@@ -34,9 +34,8 b' REVLOG_DEFAULT_VERSION = REVLOG_DEFAULT_'
 REVLOGNG_FLAGS = REVLOGNGINLINEDATA | REVLOGSHALLOW
 
 # revlog index flags
-REVIDX_PARENTDELTA  = 1
 REVIDX_PUNCHED_FLAG = 2
-REVIDX_KNOWN_FLAGS = REVIDX_PUNCHED_FLAG | REVIDX_PARENTDELTA
+REVIDX_KNOWN_FLAGS = REVIDX_PUNCHED_FLAG
 
 # max size of revlog with inline data
 _maxinline = 131072
@@ -223,7 +222,6 b' class revlog(object):'
         self._chunkcache = (0, '')
         self.index = []
         self._shallowroot = shallowroot
-        self._parentdelta = 0
         self._pcache = {}
         self._nodecache = {nullid: nullrev}
         self._nodepos = None
@@ -233,8 +231,6 b' class revlog(object):'
             v = opener.options['defversion']
             if v & REVLOGNG:
                 v |= REVLOGNGINLINEDATA
-            if v & REVLOGNG and 'parentdelta' in opener.options:
-                self._parentdelta = 1
 
         if shallowroot:
             v |= REVLOGSHALLOW
@@ -834,11 +830,8 b' class revlog(object):'
         self._chunkcache = (0, '')
 
     def deltaparent(self, rev):
-        """return previous revision or parentrev according to flags"""
-        if self.flags(rev) & REVIDX_PARENTDELTA:
-            return self.parentrevs(rev)[0]
-        else:
-            return rev - 1
+        """return deltaparent of the given revision"""
+        return rev - 1
 
     def revdiff(self, rev1, rev2):
         """return or calculate a delta between two revisions"""
@@ -870,16 +863,10 b' class revlog(object):'
 
         # build delta chain
         chain = []
-        index = self.index # for performance
         iterrev = rev
-        e = index[iterrev]
         while iterrev != base and iterrev != cachedrev:
             chain.append(iterrev)
-            if e[0] & REVIDX_PARENTDELTA:
-                iterrev = e[5]
-            else:
-                iterrev -= 1
-            e = index[iterrev]
+            iterrev -= 1
         chain.reverse()
         base = iterrev
 
@@ -1018,11 +1005,6 b' class revlog(object):'
         # should we try to build a delta?
         if prev != nullrev:
             d = builddelta(prev)
-            if self._parentdelta and prev != p1r:
-                d2 = builddelta(p1r)
-                if d2 < d:
-                    d = d2
-                    flags = REVIDX_PARENTDELTA
             dist, l, data, base = d
 
         # full versions are inserted when the needed deltas