store: return just one filename in walk functions Various walk functions return `(revlog_type, decoded, encoded)` where decoded could be None. But no-one cares about `encoded` and expects `unencoded` to be present, except verify (because this can only happen with old repo formats). Simplify all this by either failing outright if a decoding a filename fails (instead of almost certainly failing with a type error due to treating None as a bytes), or skipping the filename but providing in an out argument for hg verify. Differential Revision: https://phab.mercurial-scm.org/D11248

--- a/mercurial/upgrade_utils/engine.py	Sun Aug 01 10:57:21 2021 -0400
+++ b/mercurial/upgrade_utils/engine.py	Mon Aug 02 08:05:13 2021 -0400
@@ -201,7 +201,7 @@
 
     # Perform a pass to collect metadata. This validates we can open all
     # source files and allows a unified progress bar to be displayed.
-    for rl_type, unencoded, encoded, size in alldatafiles:
+    for rl_type, unencoded, size in alldatafiles:
         if not rl_type & store.FILEFLAGS_REVLOG_MAIN:
             continue