Allow using --exclude without also specifying --workspace.

[xStrom]

We're using cargo-hack at Linebender, in ~15 repositories and growing. Thanks for your continued maintenance of this project!

In order for us to maintain CI scripts across that many repositories, we try to write them in a super generic way. So that we can mostly copy-paste the script and only have minimal configuration variables per repository.

For example, one set of variables we currently have for Xilem is:

# List of packages that will be checked with the minimum supported Rust version.
RUST_MIN_VER_PKGS: "-p xilem -p xilem_core -p masonry"
# List of packages that can not target Wasm.
NO_WASM_PKGS: "--exclude masonry --exclude xilem"

So for the MSRV job we reference RUST_MIN_VER_PKGS instead of --workspace and for the Wasm job we add NO_WASM_PKGS. Works well. However a complication arises with the MSRV Wasm job! Because the combination of -p xilem -p xilem_core -p masonry --exclude masonry --exclude xilem does not currently work with cargo-hack.

Our current solution is to just have a third variable:

# RUST_MIN_VER_PKGS - NO_WASM_PKGS, evaluated.
RUST_MIN_VER_WASM_PKGS: "-p xilem_core"

It works, of course. However it would be nice to not have to keep this additional variable in sync, especially across all our repositories.

This PR here addresses the problem at the cargo-hack level by removing the requirement to also specify --workspace when using --exclude. This works nicely and allows us to remove that extra variable and skip the work of maintaining it for each repository.

[taiki-e]

Looks good, thanks @xStrom!

[taiki-e]

Published in 0.6.33.