Add flag to specify filename other than CODENOTIFY

[pdubroy]

Context

For RFC 551 APPROVED: Documenting ownership with OWNERS files, we are adding the ability to specify OWNERS of certain files/directories in our code base. We want this to behave in basically the exact same way as CODENOTIFY. However, being listed in CODENOTIFY doesn't necessarily mean you are an owner, so we need to keep the two lists separate.

As discussed in OWNERS in Sourcegraph: Implementation details, there aren't any off-the-shelf solutions that would do exactly what we want. In fact, Codenotify is the closest thing — so I decided to modify it slightly so that it can read OWNERS files as well as CODENOTIFY files.

This has the advantage that we would only have one tool and one file format to support for these two very similar purposes.

Changes in this PR

• Add a -filename option to the codenotify tool, with a default value of "CODENOTIFY".
• Modify the Markdown output slightly to account for the possibility of different file names.
• Add an input to the GitHub workflow, which allows users of the workflow to pass in a different value for the filename.

[pdubroy]

@jhchabran Please take a look for early feedback. There's something not quite right about how I'm passing the parameter through from the GitHub action, but I'd like to get your feedback on the other aspects while I continue to debug that. Thanks!

[sourcegraph-bot]

Codenotify: Notifying subscribers in CODENOTIFY files for diff 515c85d...493cbc5.

Notify	File(s)
@nicksnyder	action.yml main.go main_test.go

[jhchabran]

Nice 👍!

I added some comments, which provide two possible ways to simplify the logic around passing the filename from GitHub actions.

I tend to prefer the first one (where we are using the binary as the entry point and using CMD to pass additional args to overrides the defaults, but I don't have a strong opinion either.

[bobheadxi]

I like this approach! Code LGTM as well :)

[nicksnyder]

Happy to see you all running with this! This codebase was a bit of a hack project for me so feel free to take it from here and change whatever you want. I'll stay out of the code reviews unless you explicitly tag me :)