diff mercurial/interfaces/repository.py @ 47077:119790e1c67c

cg4: introduce protocol flag to signify the presence of sidedata

We need a way of signaling whether the current revision has sidedata or not,
and re-using the revision flags would waste potential revlog flags and mix two
normally independent layers.

In this change, we add a single byte at the start of the ch4 delta header to
set potential protocol flags. We also reclaim the revlog flag for sidedata,
since it is no longer used, in its place now lives the (also experimental)
copytracing flag.

When generating deltas, apply the `CG_FLAG_SIDEDATA` flag if there is sidedata.
When applying the deltas, if said flag is present, the next chunk contains the
sidedata.

Differential Revision: https://phab.mercurial-scm.org/D10343

--- a/mercurial/interfaces/repository.py	Thu Apr 08 16:34:11 2021 +0200
+++ b/mercurial/interfaces/repository.py	Sat Apr 10 11:27:40 2021 +0200
@@ -27,14 +27,12 @@
 REVISION_FLAG_CENSORED = 1 << 15
 REVISION_FLAG_ELLIPSIS = 1 << 14
 REVISION_FLAG_EXTSTORED = 1 << 13
-REVISION_FLAG_SIDEDATA = 1 << 12
-REVISION_FLAG_HASCOPIESINFO = 1 << 11
+REVISION_FLAG_HASCOPIESINFO = 1 << 12
 
 REVISION_FLAGS_KNOWN = (
     REVISION_FLAG_CENSORED
     | REVISION_FLAG_ELLIPSIS
     | REVISION_FLAG_EXTSTORED
-    | REVISION_FLAG_SIDEDATA
     | REVISION_FLAG_HASCOPIESINFO
 )
 
@@ -457,6 +455,13 @@
         """Raw sidedata bytes for the given revision."""
     )
 
+    protocol_flags = interfaceutil.Attribute(
+        """Single byte of integer flags that can influence the protocol.
+
+        This is a bitwise composition of the ``storageutil.CG_FLAG*`` constants.
+        """
+    )
+
 
 class ifilerevisionssequence(interfaceutil.Interface):
     """Contains index data for all revisions of a file.