Update CoverageMapping Format Version requirements

[Swatinem]

This is the companion to rust-lang/rust#90047.

r? @richkadel

[richkadel]

Hey @Swatinem ! Exciting to see an upgrade here. Thank you.

I'm taking a look at the devguide first, which I see is a small change.

There's one issue, but it raises the question, why upgrade to version 5 and not 6?

[richkadel]

Version 5 is not the "most current version". The most current version is version 6.

(But I am wondering why not upgrade to version 6 and skip 5.)

[Swatinem]

Good point, might as well jump to v6. I was under the impression that we should keep compatibility with lower versions as much as we can to get the features we need.

Also, I haven’t looked at it in too much detail yet, so I don’t know yet if the v6 changes need other code changes as well.

[richkadel]

The description here makes it sound like a minor change, but please take a look and update this thread if it appears more complex than that.

[richkadel]

cc: @tmandry @wesleywiser

[Swatinem]

@richkadel I updated to v6. The format is backwards compatible if you only use absolute filenames.
See rust-lang/llvm-project@5fbd1a3#diff-d1da015180caa93a34599914b8a918220740263cec7756718f3762bd0d9a4abaR158-R174
I still pushed an empty filename as the first one.

[richkadel]

Since I will be OOO for 3 weeks, please ask @tmandry or @wesleywiser to review, when you are ready. Thanks again for these contributions!

[camelid]

Could you add a machine-checkable date comment?

Suggested change

	[^llvm-and-covmap-versions]: The Rust compiler (as of
	[^llvm-and-covmap-versions]: The Rust compiler (as of <!-- date: 2021-11 -->

[richkadel]

I made this change in the revised PR #1267.

[richkadel]

@Swatinem - Feel free to close this PR in favor of #1267. I reviewed your changes in creating the revised PR (very helpful, thanks!) and applied the changes and review recommendations.