upgrade: introduce the internal code for revlog cloning selection

upgrade: introduce the internal code for revlog cloning selection

For now we still clone every single revlogs but all the selection mechanism is
now in place in the lower layer.

The next changesets will introduce the user interface part of the selection.

--- a/mercurial/upgrade.py	Tue Jul 30 19:58:44 2019 +0200
+++ b/mercurial/upgrade.py	Thu Aug 01 03:15:58 2019 +0200
@@ -562,7 +562,26 @@
             or unencodedname.endswith('00manifest.i')):
         destrepo.svfs.fncache.add(unencodedname)
 
-def _clonerevlogs(ui, srcrepo, dstrepo, tr, deltareuse, forcedeltabothparents):
+UPGRADE_CHANGELOG = object()
+UPGRADE_MANIFEST = object()
+UPGRADE_FILELOG = object()
+
+UPGRADE_ALL_REVLOGS = frozenset([UPGRADE_CHANGELOG,
+                                 UPGRADE_MANIFEST,
+                                 UPGRADE_FILELOG])
+
+def matchrevlog(revlogfilter, entry):
+    """check is a revlog is selected for cloning
+
+    The store entry is checked against the passed filter"""
+    if entry.endswith('00changelog.i'):
+        return UPGRADE_CHANGELOG in revlogfilter
+    elif entry.endswith('00manifest.i'):
+        return UPGRADE_MANIFEST in revlogfilter
+    return UPGRADE_FILELOG in revlogfilter
+
+def _clonerevlogs(ui, srcrepo, dstrepo, tr, deltareuse, forcedeltabothparents,
+                  revlogs=UPGRADE_ALL_REVLOGS):
     """Copy revlogs between 2 repos."""
     revcount = 0
     srcsize = 0
@@ -643,7 +662,6 @@
             continue
 
         oldrl = _revlogfrompath(srcrepo, unencoded)
-        newrl = _revlogfrompath(dstrepo, unencoded)
 
         if isinstance(oldrl, changelog.changelog) and 'c' not in seen:
             ui.write(_('finished migrating %d manifest revisions across %d '
@@ -682,11 +700,19 @@
             progress = srcrepo.ui.makeprogress(_('file revisions'),
                                                total=frevcount)
 
+        if matchrevlog(revlogs, unencoded):
+            ui.note(_('cloning %d revisions from %s\n')
+                    % (len(oldrl), unencoded))
+            newrl = _revlogfrompath(dstrepo, unencoded)
+            oldrl.clone(tr, newrl, addrevisioncb=oncopiedrevision,
+                        deltareuse=deltareuse,
+                        forcedeltabothparents=forcedeltabothparents)
+        else:
+            msg = _('blindly copying %s containing %i revisions\n')
+            ui.note(msg % (unencoded, len(oldrl)))
+            _copyrevlog(tr, dstrepo, oldrl, unencoded)
 
-        ui.note(_('cloning %d revisions from %s\n') % (len(oldrl), unencoded))
-        oldrl.clone(tr, newrl, addrevisioncb=oncopiedrevision,
-                    deltareuse=deltareuse,
-                    forcedeltabothparents=forcedeltabothparents)
+            newrl = _revlogfrompath(dstrepo, unencoded)
 
         info = newrl.storageinfo(storedsize=True)
         datasize = info['storedsize'] or 0
@@ -746,7 +772,8 @@
     before the new store is swapped into the original location.
     """
 
-def _upgraderepo(ui, srcrepo, dstrepo, requirements, actions):
+def _upgraderepo(ui, srcrepo, dstrepo, requirements, actions,
+                 revlogs=UPGRADE_ALL_REVLOGS):
     """Do the low-level work of upgrading a repository.
 
     The upgrade is effectively performed as a copy between a source
@@ -775,7 +802,7 @@
 
     with dstrepo.transaction('upgrade') as tr:
         _clonerevlogs(ui, srcrepo, dstrepo, tr, deltareuse,
-                     're-delta-multibase' in actions)
+                      're-delta-multibase' in actions, revlogs=revlogs)
 
     # Now copy other files in the store directory.
     # The sorted() makes execution deterministic.