Support for Slack mentions

[phongulus]

Description of the task

Basic support for Slack mentions. When a GitHub handle can be matched with a Slack email, the Slack user is mentioned in Monorobot's messages and unfurled links (only links from supported repos).

The matching is done by

• removing all hyphens, dots from the GitHub handle and lowercase-ing.
• canonicalising the Slack email address, removing hyphens, removing the email domain, lowercase.

Monorobot keeps a cache of the Slack user list that's refreshed every 24 hours. Alternatively, GitHub handle to Slack email mapping can also be manually injected in .monorobot.json under user_mappings - in the case of conflicting mappings, the mapping in .monorobot.json takes precedence.

If Monorobot can't match a Slack user in the cached mapping, they are not mentioned.

How to test

Some basic tests were added. Test with

make runtest

Old tests should remain the same, as the GitHub handles there are not present in the Slack user list cache file.

References

• existing issue: Map gh usernames with slack usernames #47

[phongulus]

This is what the mentions look like right now:

Monorobot messages:

Unfurled links:

Mentions in the author_name field of unfurls don't get properly decoded by Slack, so I'm putting them in pretext.

[phongulus]

Rolled back mentions in push/commit notifications @yasunariw @tysg. Now things look like this:

[glionnet]

Option.map_default ? or is it done like this for readability ?

[phongulus]

I don't remember, but I suppose the current match statement would look a bit cleaner since using Option.map_default would look something like this:

let slack_mention =
    author
    |> Option.map_default
        (fun gh_user -> gh_user |> match_github_user_to_slack_id |> Slack.format_slack_mention)
        ""

[rr0gi]

(please cleanup the commits / squash before merge)

[yasunariw]

I think the test harness should be modified to refresh the context with a handcrafted mapping (in OCaml, not from file) for some github/slack profiles in the existing test cases

I would prefer to update the output of the existing test cases with the changes from this feature, not to create new ones

[phongulus]

I think it's probably a good idea to have a separate file for Slack profiles, since we'd probably want to test with an actual Slack users.list payload. I don't think the existing test cases have any message body with GitHub user mentions either, so we should keep some of the new test files.

[yasunariw]

thanks! lgtm, let's cleanup commits and merge

[rr0gi]

this behaviour should be mentioned in readme please