Docs say --remap-path-prefix treats paths as strings during matching but compiler does not

[michaelwoerister]

Our --remap-path-prefix documentation says "The
replacement is purely textual, with no consideration of the current system's
pathname syntax.". But that currently is not the case. Prefix matching is implemented via Path::strip_prefix which can behave quite differently:

`abc` is a prefix of `abc/def`
`abc/.` is a prefix of `abc/def`
`ab` is NOT a prefix of `abc/def`
`abc` is NOT a prefix of `./abc/def`
`./abc` is NOT a prefix of `abc/def`
`./abc` is a prefix of `./abc/def`

It's unclear whether we should update the documentation or change the compiler's behavior.

rustc --version --verbose:

rustc 1.60.0 (7737e0b5c 2022-04-04)
binary: rustc
commit-hash: 7737e0b5c4103216d6fd8cf941b7ab9bdbaace7c
commit-date: 2022-04-04
host: x86_64-unknown-linux-gnu
release: 1.60.0
LLVM version: 14.0.0

[ehuss]

It looks like string-based matching was incidentally removed in #46335. I probably missed that when writing the docs, instead relying on your comment here. Do you recall at the time if the preference was for simplicity of implementation, or simplicity for the user?

[michaelwoerister]

If I remember correctly the original argument for doing things on a string basis was that it's more predictable for the user. But I'm not sure if that's actually true.