Fix a commit hook issue with the initial commit to Mercurial repositories

Summary:
Fixes T4257. The `hg heads` command exits with an error code and no output in an empty repository.

Just ignore the error code: we don't have a great way to distinguish between errors, and we ran another `hg` command moments before, so we have at least some confidence it isn't a PATH sort of thing.

Test Plan: Created a new Mercurial repository and pushed to hit the error in T4257. Applied this fix and got a clean push with an accurate push log.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4257

Differential Revision: https://secure.phabricator.com/D7817
Make `repository pull` install hooks the first time

Summary:
Ref T4257. Currently, the pull logic looks like this:

  if (new) {
    create();
  } else {
    if (hosted) {
      install_hooks();
    } else {
      update();
    }
  }

This means that the first time you run `repository pull`, hooks aren't installed, which makes debugging trickier. Instead, reorganize the logic:

  if (new) {
    create();
  } else {
    if (!hosted) {
      update();
    }
  }

  if (hosted) {
    install_hooks();
  }

Test Plan: Ran `bin/repository pull` on a new `hg` repo and got hooks installed immediately.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4257

Differential Revision: https://secure.phabricator.com/D7818
Make conduit certificate readonly and select-on-click

Summary: See comments in <https://secure.phabricator.com/D6331#comment-3> -- make the Conduit Token and Conduit Certificate interfaces readonly and select-on-click.

Test Plan:
  - Viewed `/conduit/token/`, verified it was readonly and selected on click.
  - Viewed `/settings/panel/conduit/`, likewise.

Reviewers: Avish, btrahan, wotte

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7819