In previous patches, we have added an internal API to unhide hidden changesets.
This patch makes the following command use that api in nowarn mode i.e. there
will be no warning while accessing hidden changesets.
cat, diff, export, files, heads, identify, log, manifest, parents, status
This patch also adds test demonstarting the behaviour.
.. feature:: Accessing hidden changesets
Set config option 'experimental.directaccess = True' to access hidden changesets from read only commands.