Summary:
This diff makes the following modifications to the (former) `hiddenhash` extension:
- Makes the error messages configurable, allowing us to easily change the error messages in `facebook.rc`.
- Renames the extension to `hiddenerror`, since the primary feature is now the configurable error messages rather than using a hash in the message.
- Changes the method by which the extension wraps the `changectx` constructor. The old method of wrapping would result in errors in code paths that in `context.py` that performed `isinstance()` checks on contexts.
Test Plan: To test arc patch this extension into your `facebook-hg-rpms` and enable it for a test repo. Then, attempt to access a hidden node. You should see the default error message defined in the extension. Setting `hiddenerror.message` and `hiddenerror.hint` should allow you to customize the messages. See test file for examples.
Reviewers: #mercurial, rmcelroy
Reviewed By: rmcelroy
Subscribers: rmcelroy, durham, mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D4548140
Tasks: 15896355
Signature: t1:4548140:1487063552:06395c1eaaa83b00ead8e80e2cd8f9d13f7d08e2
