cargo --fix does not recognise there's a VCS on a fossil project

[bingen13]

Problem

After running cargo --build, it offered suggestions to fix issues via cargo --fix. However, cargo --fix does not recognise the project is versioned by fossil, although it was created with the appropriate cargo new option.

Steps

1. Create a project version by fossil: cargo new example --vcs fossil
2. Run cargo fix on it: cargo fix

Possible Solution(s)

No response

Notes

No response

Version

cargo 1.72.1 (103a7ff2e 2023-08-15)

[weihanglo]

There is indeed very limited to VCS support in cargo fix command — only Git and Mecurial are supported at this moment, and only Git got the ability to detect dirty state. The logic was implemented here:

cargo/src/cargo/ops/fix.rs

Lines 150 to 156 in 5bf83d8

	if !existing_vcs_repo(config.cwd(), config.cwd()) {
	bail!(
	"no VCS found for this package and `cargo fix` can potentially \
	perform destructive changes; if you'd like to suppress this \
	error pass `--allow-no-vcs`"
	)
	}

I am not quite sure if we want to add the support to cargo fix, although it doesn't seem to have alternative approach.

FWIW, here is a summary of previous discussions about “VCS support”.