Implement --remap-path-prefix

[jsgf]

Remove experimental -Zremap-path-prefix-from/to, and replace it with
the stabilized --remap-path-prefix=from=to variant.

Implementation for #41555

[rust-highfive]

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[michaelwoerister]

The evaluation of components in tuple constructors is probably defined, but I still find this hard to read. And it's probably the wrong order because the iterator starts at the end :) Could you rewrite this to something like:

letmut parts = ...;let to = parts.next();let from = parts.next();match(from, to){ ...}

[jsgf]

Is there anything that implements FromIterator<Item=T> for Option<(T,...)>? I keep ending up in situations where it would be useful (mostly parsing with split), but I suspect it would clash with an existing FromIterator for Option<T> (unless specialization helps?).

[michaelwoerister]

Thanks a lot, @jsgf! The implementation looks good to me, with the bug fixed.

I think we also need to update some documentation, right @rust-lang/docs? There's an entry for the feature in the unstable book. Where should this be moved to?

[jsgf]

Yes, documentation was my next question.

[jsgf]

Removed unstable book documentation and updated rustc.1 man page, which seems to be the only place I could find written documentation on command-line options.

[steveklabnik]

Yes, for now that's true. We haven't created a space for rustc docs yet; we wanted to.

[michaelwoerister]

Alright then: @bors r+

Thanks for pushing this over the finish line, @jsgf!

@rust-lang/core, @rust-lang/compiler, @rust-lang/dev-tools: We are stabilizing path prefix remapping!

[bors]

📌 Commit ffd8ea7 has been approved by michaelwoerister

[jsgf]

Ah, I just found a problem - it looks like having this option on the command line changes the crate hash.

[jsgf]

Looks like #48019/#48162 is still an issue.

[jsgf]

Rebasing to master seems to have fixed it, so maybe I just didn't have the other change before.

[sanxiyn]

@bors r+

[bors]

📌 Commit 56a6828 has been approved by sanxiyn