Mask colons in segment paths

[lefou]

Again a Windows thing, but the evaluator paths should not contain colons. We mask them with $colon.

Fix #2923

[lihaoyi]

Since we're escaping things with $, should we also mask $ with $$ to avoid potential conflicts?

[lefou]

Since we're escaping things with $, should we also mask $ with $$ to avoid potential conflicts?

Can you a bit more specific? What do we mask with $ and which conflicts do you expect with this concrete $colon?

[lefou]

@lihaoyi Did you mean the name mangling for private inner classes in Scala? Or something else?

I think the masking I introduce here doesn't need to be bijective. It's only from segment path to file path. So, the question is, will two different segment paths project to the same file path?

[lihaoyi]

@lefou oh I wasn't thinking about Scala compiler name mangling, I was more thinking about potential collisions caused by Mill's own mangling. Like if we have two tasks, with names a:b and a$colonb, they would collide unless we escaped the $ such that a$colonb becomes a$$colonb

This isn't an edge case likely to cause any issues in practice, but it's definitely a thing