revlog: decouple caching from addrevision callback for addgroup

For changesets, it is useful to cache the content as it will almost
always be processed afterwards. For manifests on the other hand, the
content is often not used directly as there is a fast path for deltas.
Explicitly disable the cache in exchangev2's manifest handling for that
reason.

Differential Revision: https://phab.mercurial-scm.org/D9847

mercurial/changegroup.py

@@ -334,6 +334,7 b' class cg1unpacker(object):'
                 deltas,
                 csmap,
                 trp,
+                alwayscache=True,
                 addrevisioncb=onchangelog,
                 duplicaterevisioncb=ondupchangelog,
             ):

mercurial/exchangev2.py

@@ -423,6 +423,7 b' def _processchangesetdata(repo, tr, objs'
         iterrevisions(),
         linkrev,
         weakref.proxy(tr),
+        alwayscache=True,
         addrevisioncb=onchangeset,
         duplicaterevisioncb=ondupchangeset,
     )

mercurial/interfaces/repository.py

@@ -769,7 +769,13 b' class ifilemutation(interfaceutil.Interf'
         ``nullid``, in which case the header from the delta can be ignored
         and the delta used as the fulltext.
 
+        ``alwayscache`` instructs the lower layers to cache the content of the
+        newly added revision, even if it needs to be explicitly computed.
+        This used to be the default when ``addrevisioncb`` was provided up to
+        Mercurial 5.8.
+
         ``addrevisioncb`` should be called for each node as it is committed.
+        ``duplicaterevisioncb`` should be called for each pre-existing node.
 
         ``maybemissingparents`` is a bool indicating whether the incoming
         data may reference parents/ancestor revisions that aren't present.

mercurial/manifest.py

@@ -1836,6 +1836,7 b' class manifestrevlog(object):'
         deltas,
         linkmapper,
         transaction,
+        alwayscache=False,
         addrevisioncb=None,
         duplicaterevisioncb=None,
     ):
@@ -1843,6 +1844,7 b' class manifestrevlog(object):'
             deltas,
             linkmapper,
             transaction,
+            alwayscache=alwayscache,
             addrevisioncb=addrevisioncb,
             duplicaterevisioncb=duplicaterevisioncb,
         )

mercurial/revlog.py

@@ -2375,6 +2375,7 b' class revlog(object):'
         deltas,
         linkmapper,
         transaction,
+        alwayscache=False,
         addrevisioncb=None,
         duplicaterevisioncb=None,
     ):
@@ -2475,7 +2476,7 b' class revlog(object):'
                     (baserev, delta),
                     ifh,
                     dfh,
-                    alwayscache=bool(addrevisioncb),
+                    alwayscache=alwayscache,
                     deltacomputer=deltacomputer,
                 )
 

mercurial/unionrepo.py

@@ -128,6 +128,7 b' class unionrevlog(revlog.revlog):'
         deltas,
         linkmapper,
         transaction,
+        alwayscache=False,
         addrevisioncb=None,
         duplicaterevisioncb=None,
         maybemissingparents=False,