adds --path and --nonexistent options to "rustup override unset"; adds hint to "rustup override list output" (as discussed in #642)

[Riateche]

No description provided.

[brson]

Awesome. Thanks @Riateche ! Reviewing now.

[brson]

Please move this text to help.rs.

"toolchain for specified directory" -> "toolchain for the specified directory"

"toolchain for current directory" -> "toolchain for the current directory"

[brson]

Looks great!

[brson]

This calls for several tests.

Can you add tests for rustup override list with a nonexistant directory, rustup override unset --path with both existing and non-existing dirs, rustup override unset --nonexistent, and similar cases for rustup override remove? They can go in tests/cli-exact.rs and crib off the existing tests there.

[Riateche]

I'm a bit stuck with tests. I don't want to write fully duplicated tests for "remove" and "unset" because they should be complete aliases. But when I attempt to move test implementation to a function, it suddenly stops working, although nothing else is changed:

fn remove_override_test_helper(keyword: &'static str) {
    setup(&|config| {
        let cwd = env::current_dir().unwrap();
        expect_ok(config, &["rustup", "override", "add", "nightly"]);
        expect_ok_ex(config, &["rustup", "override", keyword],
            r"",
            &format!(r"info: override toolchain for '{}' removed
            ", cwd.display()));
    });

}

#[test]
fn remove_override() {
    remove_override_test_helper("remove");
}

Output:

failures:

---- remove_override stdout ----
    out.ok: true
out.stdout:


  nightly-x86_64-unknown-linux-gnu installed - 1.3.0 (hash-n-2)


out.stderr:

info: syncing channel updates for 'nightly-x86_64-unknown-linux-gnu'
info: downloading component 'rust-std'
info: downloading component 'rustc'
info: downloading component 'cargo'
info: downloading component 'rust-docs'
info: installing component 'rust-std'
info: installing component 'rustc'
info: installing component 'cargo'
info: installing component 'rust-docs'
info: override toolchain for '/home/ri/rust/forks/rustup.rs' set to 'nightly-x86_64-unknown-linux-gnu'

expected: 
out.ok: true
out.stdout:


out.stderr:

info: override toolchain for '/home/ri/rust/forks/rustup.rs' removed

expected.stdout: 


expected.stderr: 

info: override toolchain for '/home/ri/rust/forks/rustup.rs' removed

thread 'remove_override' panicked at 'err ["rustup", "override", "remove"]', src/rustup-mock/src/clitools.rs:206
note: Run with `RUST_BACKTRACE=1` for a backtrace.


failures:
    remove_override

Next, I will need to create temporary directories to perform some tests. Is it ok to create them in the current directory or should I create them somewhere else?

[brson]

For temporary directories please use the tempdir crate. It's already a dependency of rustup, but needs to be added to dev-dependencies.

The error with the test is frustrating - the output looks write. The rustup test harness is fairly primitive and can be hard to interpret. If you push the non-working commits I can take a look.

[Riateche]

Looks like it was just white space mismatch caused by code formatting. It seems to be working now. I'll try to write new tests.

[Riateche]

I've created all needed tests. I had to remove "canonicalize" call when removing nonexistent path. otherwise it produced a warning. Now Travis says there is an error on Mac OS. It may be related to "canonicalize" call because paths do not match. I don't have Mac OS so I can't fix it quickly. Maybe you can take a look.

[Riateche]

Looks like I got it working. Please review.

[brson]

Woo! Thanks @Riateche ! Thank you so much for sticking it out and writing those tests. I <3 tests.