This patch provides a way for the CI to make sure a given patch is
rebased on master, smoke tested, and still landed as the submitter as one
would normally expect from a landing workflow.
The land workflow, once complete, will be roughly this:
1. User runs `arc land`
2. A custom ABC Arcanist workflow intercepts the `land` command and diverts it to `abc-land` workflow rather than the default.
The default workflow will still be available under another name, if needed.
3. The `abc-land` workflow sends the REVISION and encrypted CONDUIT_TOKEN to abcbot.
4. abcbot queues the build.
5. The build decrypts CONDUIT_TOKEN and runs `land-patch.sh`
Some parts are obviously missing, but these will come later:
* Applying autogen onto a patch in-flight, such as updating manpages
* Being able to land unreviewed diffs (reserved for automated commits such as updating chainparams).
Regarding the CONDUIT_TOKEN, note that the script needs it unencrypted in order to land the patch
as you. This is safe to run locally. For the complete land-bot pipeline, your Conduit token will
be encrypted before passing along via `arc land`. This prevents the token from accidentally
getting logged while your request is on its journey through abcbot and the patch queue. It will only
be unencrypted once the land-bot begins working on your patch, immediately before calling this script.
While this infra is being worked on, feel free to run this script directly and provide additional feedback.