sidedata: return enough data to set the proper flag in the future

If the revision has information relevant to copy tracing, we need to set a
dedicated flag in revlog. Currently the upgrade process is failing to do so.
Before we teach the upgrade process about flags, we make the information
available where we will needs it.

Differential Revision: https://phab.mercurial-scm.org/D9198

mercurial/metadata.py

@@ -803,7 +803,7 b' def decode_files_sidedata(sidedata):'
 def _getsidedata(srcrepo, rev):
     ctx = srcrepo[rev]
     files = compute_all_files_changes(ctx)
-    return encode_files_sidedata(files)
+    return encode_files_sidedata(files), files.has_copies_info
 
 
 def getsidedataadder(srcrepo, destrepo):
@@ -881,18 +881,19 b' def _get_worker_sidedata_adder(srcrepo, '
     staging = {}
 
     def sidedata_companion(revlog, rev):
-        sidedata = {}
+        data = {}, False
         if util.safehasattr(revlog, b'filteredrevs'):  # this is a changelog
             # Is the data previously shelved ?
             sidedata = staging.pop(rev, None)
             if sidedata is None:
                 # look at the queued result until we find the one we are lookig
                 # for (shelve the other ones)
-                r, sidedata = sidedataq.get()
+                r, data = sidedataq.get()
                 while r != rev:
-                    staging[r] = sidedata
+                    staging[r] = data
                     r, sidedata = sidedataq.get()
             tokens.release()
+        sidedataq, has_copies_info = data
         return False, (), sidedata
 
     return sidedata_companion
@@ -906,7 +907,7 b' def _get_simple_sidedata_adder(srcrepo, '
     def sidedatacompanion(revlog, rev):
         sidedata = {}
         if util.safehasattr(revlog, 'filteredrevs'):  # this is a changelog
-            sidedata = _getsidedata(srcrepo, rev)
+            sidedata, has_copies_info = _getsidedata(srcrepo, rev)
         return False, (), sidedata
 
     return sidedatacompanion