Define an MSRV policy for the crate

[zslayton]

          > while we still can

There's a cfg_version RFC that will help with this.

Also, if we haven't already done so, we should define a MSRV policy for this crate.

Originally posted by @popematt in #796 (comment)

[zslayton]

I propose stealing the MSRV policy from the jiff crate, as it seems reasonable to me:

This crate's minimum supported rustc version is 1.70.0.

The policy is that the minimum Rust version required to use this crate can be increased in minor version updates. For example, if jiff 1.0 requires Rust 1.20.0, then jiff 1.0.z for all values of z will also require Rust 1.20.0 or newer. However, jiff 1.y for y > 0 may require a newer minimum version of Rust.

[popematt]

@zslayton, would it be fair to summarize that as "increasing the MSRV requires a new minor version"?

Another one that looks reasonable to me is this proposal for libc.

[zslayton]

would it be fair to summarize that as "increasing the MSRV requires a new minor version"?

Yes, without a "we support the last N releases" requirement. I could get behind a "last N" policy for a sufficiently small N.