Tell GitHub that .sccignore is an ignore list

[spenserblack]

This is a super-nitpicky PR, because I like to see syntax highlighting when I look at a file 😅 I think you're already familiar with linguist, but just to describe what this PR does:

• Applies Ignore List syntax highlighting to .sccignore
• If for whatever reason you decided to include Ignore List stats in the GitHub language bar, .sccignore would be counted to that.

[boyter]

Thanks for the PR. Merged. I should look into how linguist does this more as something similar for scc might make it more useful for integrations.

[spenserblack]

Regarding how Linguist does it, I don't think it does much more than a case insensitive match to one of its language's names or its aliases. It does parse out the .gitattributes (using git2 IIRC) but, for SCC, IDK if .gitattributes should be the "official" place to set language overrides. Linguist is very special in that it's used for GitHub and analyzes Git revisions, not files (e.g. you can delete all your files from your repo and still use it). So it makes a lot of sense to tightly couple with Git tools. Since SCC is more generic, and isn't Git-specific, perhaps it can pioneer a more generic .attributes file (or .sccattributes)? But you also have the freedom to do something completely different.

I'm going on a bit of a rant, but I just want to make the point that, while Linguist is certainly a very cool tool, what's best for Linguist might not be best for SCC.

[spenserblack]

Oh, just an FYI that the generic .ignore will be handled by github-linguist/linguist#7070, so you don't need to worry about that.