Document minimum required version of Rust + Cargo in README

[mozilla]

Document minimum required version of Rust + Cargo in README

[luser]

You should be able to simply run cargo build to build the binary, or cargo build --release if you want an optimized binary. The build-release script is just what I use to build release binaries locally, it depends on some quirky things.

Once I get a few more things together I'd like to publish prebuilt binaries via GitHub releases, which should make things simpler for people.

[andreparodi]

thanks @luser

didn't realise that was the standard build command for rust. thanks.

i face a different problem now.

'''
andrep@bardtw2827 ~/dev/sccache (master) $ cargo -V
cargo 0.8.0 (built 2016-03-22)
andrep@bardtw2827 ~/dev/sccache (master) $ cargo build
failed to parse manifest at /home/andrep/dev/sccache/Cargo.toml

Caused by:
could not parse input as TOML
Cargo.toml:34:9 expected a key but found an empty string
Cargo.toml:34:9-34:10 expected ., but found '

'''

seems think the cfg(unix) might be causing the problem.

[luser]

I don't know specifically what version of Rust+cargo the project requires, but I've been building it locally with Rust 1.12, which ships with cargo 0.13. The build automation I set up with Travis only tests against the latest stable Rust release and nothing older, so it's entirely likely that it requires Rust 1.12 (and its matching cargo).

I'd recommend installing Rust via rustup, which makes it easy to keep your Rust toolchain up-to-date.

[luser]

It looks like support for [target.'cfg(...)'.dependencies] first shipped in cargo 0.9, so we definitely require at least that version:
rust-lang/cargo@4739ba1

[luser]

Since my change to use lru-cache we'll require Rust 1.9.0. I'll document this and add building against that version to the CI.

[luser]

Apparently futures requires Rust 1.10:
rust-lang/rust#31767

[luser]

Apparently building only requires Rust 1.10, but building tests requires Rust 1.12, because I'm using the From<T> impl for Option<T>.

[luser]

I noted that the minimum required Rust version is 1.12 in the README:
982ff32

I added builds against Rust 1.12 to the Travis CI, so we should be able to guarantee that we don't unintentionally break that.