py3: prove `hg files --rev` works

tests/test-check-py3-commands.t

@@ -14,6 +14,46 b' The full traceback is hidden to have a s'
   debuginstall
   no problems detected
 
+#if test-repo
+Make a clone so that any features in the developer's .hg/hgrc that
+might confuse Python 3 don't break this test. When we can do commit in
+Python 3, we'll stop doing this. We use e76ed1e480ef for the clone
+because it has different files than 273ce12ad8f1, so we can test both
+`files` from dirstate and `files` loaded from a specific revision.
+
+  $ hg clone -r e76ed1e480ef "`dirname "$TESTDIR"`" testrepo 2>&1 | tail -1
+  15 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+Test using -R, which exercises some URL code:
+  $ $PYTHON3 $HGBIN -R testrepo files -r 273ce12ad8f1 | tail -1
+  testrepo/tkmerge
+
+Now prove `hg files` is reading the whole manifest. We have to grep
+out some potential warnings that come from hgrc as yet.
+  $ cd testrepo
+  $ $PYTHON3 $HGBIN files -r 273ce12ad8f1
+  .hgignore
+  PKG-INFO
+  README
+  hg
+  mercurial/__init__.py
+  mercurial/byterange.py
+  mercurial/fancyopts.py
+  mercurial/hg.py
+  mercurial/mdiff.py
+  mercurial/revlog.py
+  mercurial/transaction.py
+  notes.txt
+  setup.py
+  tkmerge
+
+  $ $PYTHON3 $HGBIN files -r 273ce12ad8f1 | wc -l
+  \s*14 (re)
+  $ $PYTHON3 $HGBIN files | wc -l
+  \s*15 (re)
+  $ cd ..
+#endif
+
   $ cat > included-hgrc <<EOF
   > [extensions]
   > babar = imaginary_elephant