repository: remove storedeltachains from ifilestorage

repository: remove storedeltachains from ifilestorage

The ifilestorage interface was bootstrapped from requirements of
callers outside the storage implementation (revlogs). I believe we
even made some members public so they could be part of the interface!

Historically, the changegroup code was a gross offender when it
came to accessing low-level storage primitives. There are a handful
of members on the ifilestorage interface that are/were used only
for changegroup code.

With the recent refactor of changegroup code and the establishment
of a formal API on the storage interface for producing revision
deltas, the changegroup code is no longer accessing these low-level
primitives related to delta generation directly. Instead, things
are abstracted away in the storage implementation.

This means we can remove elements from the storage interface that
are no longer needed.

We start with "storedeltachains."

We remove it from the interface. Then we make it a private
attribute and update all references.

.. api:: storedeltachains has been dropped from ifilestorage interface

.. api:: storedeltachains on revlog classes is now _storedeltachains

Differential Revision: https://phab.mercurial-scm.org/D4227

--- a/mercurial/changelog.py	Thu Aug 09 16:02:14 2018 -0700
+++ b/mercurial/changelog.py	Thu Aug 09 16:11:24 2018 -0700
@@ -303,7 +303,7 @@
         # Delta chains for changelogs tend to be very small because entries
         # tend to be small and don't delta well with each. So disable delta
         # chains.
-        self.storedeltachains = False
+        self._storedeltachains = False
 
         self._realopener = opener
         self._delayed = False

--- a/mercurial/filelog.py	Thu Aug 09 16:02:14 2018 -0700
+++ b/mercurial/filelog.py	Thu Aug 09 16:11:24 2018 -0700
@@ -26,7 +26,6 @@
         self.filename = path
         self.index = self._revlog.index
         self.version = self._revlog.version
-        self.storedeltachains = self._revlog.storedeltachains
         self._generaldelta = self._revlog._generaldelta
 
     def __len__(self):

--- a/mercurial/repository.py	Thu Aug 09 16:02:14 2018 -0700
+++ b/mercurial/repository.py	Thu Aug 09 16:11:24 2018 -0700
@@ -723,14 +723,6 @@
         TODO this feels revlog centric and could likely be removed.
         """)
 
-    storedeltachains = interfaceutil.Attribute(
-        """Whether the store stores deltas.
-
-        TODO deltachains are revlog centric. This can probably removed
-        once there are better abstractions for obtaining/writing
-        data.
-        """)
-
     _generaldelta = interfaceutil.Attribute(
         """Whether deltas can be against any parent revision.
 

--- a/mercurial/revlog.py	Thu Aug 09 16:02:14 2018 -0700
+++ b/mercurial/revlog.py	Thu Aug 09 16:11:24 2018 -0700
@@ -627,7 +627,7 @@
         p1r, p2r = revlog.rev(p1), revlog.rev(p2)
 
         # should we try to build a delta?
-        if prev != nullrev and revlog.storedeltachains:
+        if prev != nullrev and revlog._storedeltachains:
             tested = set()
             # This condition is true most of the time when processing
             # changegroup data into a generaldelta repo. The only time it
@@ -1075,7 +1075,7 @@
             raise RevlogError(_('unknown version (%d) in revlog %s') %
                               (fmt, self.indexfile))
 
-        self.storedeltachains = True
+        self._storedeltachains = True
 
         self._io = revlogio()
         if self.version == REVLOGV0:
@@ -2995,7 +2995,7 @@
                 # cached, meaning less CPU for delta generation. There is
                 # likely room to add a flag and/or config option to control this
                 # behavior.
-                if deltaparentrev == nullrev and self.storedeltachains:
+                if deltaparentrev == nullrev and self._storedeltachains:
                     baserev = prevrev
 
                 # Revlog is configured to use full snapshot for a reason.

--- a/tests/simplestorerepo.py	Thu Aug 09 16:02:14 2018 -0700
+++ b/tests/simplestorerepo.py	Thu Aug 09 16:11:24 2018 -0700
@@ -105,7 +105,6 @@
 
         # This is used by changegroup code :/
         self._generaldelta = True
-        self.storedeltachains = False
 
         self.version = 1
 

--- a/tests/test-revlog-raw.py	Thu Aug 09 16:02:14 2018 -0700
+++ b/tests/test-revlog-raw.py	Thu Aug 09 16:11:24 2018 -0700
@@ -20,7 +20,7 @@
 
 # The test wants to control whether to use delta explicitly, based on
 # "storedeltachains".
-revlog.revlog._isgooddeltainfo = lambda self, d, textlen: self.storedeltachains
+revlog.revlog._isgooddeltainfo = lambda self, d, textlen: self._storedeltachains
 
 def abort(msg):
     print('abort: %s' % msg)
@@ -78,7 +78,7 @@
     else:
         flags = revlog.REVIDX_DEFAULT_FLAGS
     # Change storedeltachains temporarily, to override revlog's delta decision
-    rlog.storedeltachains = isdelta
+    rlog._storedeltachains = isdelta
     try:
         rlog.addrevision(text, tr, nextrev, p1, p2, flags=flags)
         return nextrev
@@ -86,7 +86,7 @@
         abort('rev %d: failed to append: %s' % (nextrev, ex))
     finally:
         # Restore storedeltachains. It is always True, see revlog.__init__
-        rlog.storedeltachains = True
+        rlog._storedeltachains = True
 
 def addgroupcopy(rlog, tr, destname=b'_destrevlog.i', optimaldelta=True):
     '''Copy revlog to destname using revlog.addgroup. Return the copied revlog.