undo-files: cleanup backup when cleaning undos

Previously, the backups were left behind, by operation cleaning the undo's like
strip, narrow and stream clone.

The remaining elevant in the room is the transaction itself, who does not
properly cleanup undo backup before copying the new ones.

mercurial/repair.py

@@ -26,6 +26,7 b' from . import ('
     phases,
     requirements,
     scmutil,
+    transaction,
     util,
 )
 from .utils import (
@@ -113,14 +114,32 b' def _collectbrokencsets(repo, files, str'
     return s
 
 
+UNDO_BACKUP = b'undo.backupfiles'
+
+
 def cleanup_undo_files(repo):
     """remove "undo" files used by the rollback logic
 
     This is useful to prevent rollback running in situation were it does not
     make sense. For example after a strip.
     """
-    # XXX need to remove the backups themselve too
-    undo_files = [(repo.svfs, b'undo.backupfiles')]
+    backup_entries = []
+    undo_files = []
+    vfsmap = repo.vfs_map
+    try:
+        with repo.svfs(UNDO_BACKUP) as f:
+            backup_entries = transaction.read_backup_files(repo.ui.warn, f)
+    except OSError as e:
+        if e.errno != errno.ENOENT:
+            msg = _(b'could not read %s: %s\n')
+            msg %= (repo.svfs.join(UNDO_BACKUP), stringutil.forcebytestr(e))
+            repo.ui.warn(msg)
+
+    for location, f, backup_path, c in backup_entries:
+        if location in vfsmap and backup_path:
+            undo_files.append((vfsmap[location], backup_path))
+
+    undo_files.append((repo.svfs, UNDO_BACKUP))
     undo_files.extend(repo.undofiles())
     for undovfs, undofile in undo_files:
         try:

tests/test-empty.t

@@ -40,7 +40,6 b' Poke at a clone:'
   hgrc
   requires
   store
-  undo.backup.branch
   wcache
 
 Should be empty (except for the "basic" requires):