Improve support of using `jj` to manage `rust-lang/rust` as a collocated git repo

[yaahc]

Right now using jj to manage the rust-lang/rust repo locally causes x tidy to fail: #128706

This is a result of jj not yet having support for .gitattributes which is responsible for adding the crlf character to the failing test.

While I would love to get that support added to jj upstream I'm assuming it is non-trivial and I'd like a better solution in the short term so I can continue to use jj while contributing to the compiler.

@jyn514 suggested I use --exclude tests/rustdoc-ui/intra-doc/warning-crlf.rs in the meantime which I'm fine with but I'd like a way to set this in my config.toml or some equivalent mechanism doesn't require manually adding this set of arguments to every invocation of x test I make.

[jyn514]

note this is essentially the same as #35678

i actually would like an even more general solution, where the flags and configs are completely interchangable and you can specify either in either place, but a solution just for exclude seems ok too.

@rustbot label T-bootstrap A-contributor-roadblock

[yaahc]

So it turns out that x test --exclude tests/rustdoc-ui/intra-doc/warning-crlf.rs won't work as a short term fix even because --exclude does not work with tidy atm.

For now I'm going with git rm tests/rustdoc-ui/intra-doc/warning-crlf.rs && git checkout HEAD !$ but I expect this to break frequently and be a source of annoyance so I'll be looking towards fixing this soon if it does in fact end up being a problem.

[sunshowers]

re crlf, as a source control expert I'd recommend never using any kind of autoconversion -- it is a bit of a nightmare to work with in too many cases.

Rather, I'd consider checking in the file with CRLFs, and disabling autoconversion so files are always checked out as-is.

(Another option is to effectively treat the file as binary content, e.g. use some other means of encoding the file, such as base64 or putting it in a tarball. But I don't know how practical that is)