transaction: rename find to findoffset and drop backup file support

transaction.find used to support access to both the regular file and
backup file list. They have different formats, so any consumer has to be
aware of the difference alredy. There is no in-core consumer for the
backup file access, so don't provide it.

Differential Revision: https://phab.mercurial-scm.org/D9276

mercurial/revlog.py

@@ -2000,12 +2000,11 b' class revlog(object):'
         ):
             return
 
-        trinfo = tr.find(self.indexfile)
-        if trinfo is None:
+        troffset = tr.findoffset(self.indexfile)
+        if troffset is None:
             raise error.RevlogError(
                 _(b"%s not found in the transaction") % self.indexfile
             )
-        troffset = trinfo[1]
         trindex = 0
         tr.add(self.datafile, 0)
 

mercurial/transaction.py

@@ -395,11 +395,9 b' class transaction(util.transactional):'
         return any
 
     @active
-    def find(self, file):
+    def findoffset(self, file):
         if file in self._map:
-            return self._entries[self._map[file]]
-        if file in self._backupmap:
-            return self._backupentries[self._backupmap[file]]
+            return self._entries[self._map[file]][1]
         return None
 
     @active