diff mercurial/exchangev2.py @ 39641:aa7e312375cf

wireprotov2: let clients drive delta behavior

Previously, the "manifestdata" and "filedata" commands assumed the
receiver had all parent revisions for requested nodes. Unless the
revision had no parents, they emitted a delta instead of a fulltext.

This strategy isn't appropriate for shallow clones and for clients
that only want to access fulltext revision data for a single node
without fetching their parent revisions.

This commit adds an "haveparents" argument to the "manifestdata"
and "filedata" commands that controls delta generation behavior.

Unless "haveparents" is set, the server assumes that the client
doesn't have parent revisions unless they were previously sent
as part of the current group of revisions.

This change allows the fulltext revision data of any individual
revision to be obtained. This will facilitate shallow clones
and other data retrieval strategies that don't require all previous
revisions of an entity to be fetched.

Differential Revision: https://phab.mercurial-scm.org/D4492

--- a/mercurial/exchangev2.py	Tue Sep 04 10:42:24 2018 -0700
+++ b/mercurial/exchangev2.py	Thu Aug 30 14:55:34 2018 -0700
@@ -283,6 +283,7 @@
                 b'tree': b'',
                 b'nodes': batch,
                 b'fields': {b'parents', b'revision'},
+                b'haveparents': True,
             }).result()
 
             # Chomp off header object.
@@ -374,7 +375,8 @@
                 fs.append((path, e.callcommand(b'filedata', {
                     b'path': path,
                     b'nodes': sorted(nodes),
-                    b'fields': {b'parents', b'revision'}
+                    b'fields': {b'parents', b'revision'},
+                    b'haveparents': True,
                 })))
 
                 locallinkrevs[path] = {