Update charlievieth/fastwalk to use forward-slashes on WSL and MSYS

[charlievieth]

This commit changes FZF to enforce that all paths are joined with forward-slashes when running on WSL (Windows Subsystem for Linux) even when the FZF binary was compiled for Windows.

Update: github.com/charlievieth/fastwalk to v1.0.5
Fixes: #3859

[charlievieth]

NOTE: This is just a draft and is incompatible with the -walker-path-sep option since (it only allows the option to force forward slashes, but does auto-detect when they're needed on WSL see: DefaultToSlash).

[junegunn]

Thanks, I wish we could avoid adding --walker-path-sep.

Defaulting to / on WSL sounds great. But we may also do that on MSYS2.

Related: sharkdp/fd#730

[junegunn]

incompatible with the -walker-path-sep option since

With this and #3909, we can safely remove --walker-path-sep.

[junegunn]

So I removed --walker-path-sep, updated the PR branch, applied the latest version of fastwalk (go get github.com/charlievieth/fastwalk@master), tested it on MSYS2, but it wasn't working as expected.

Turned out that filepath.Clean(path) is replacing / back to \ 😢

https://cs.opensource.google/go/go/+/refs/tags/go1.20.13:src/path/filepath/path.go;l=166

[junegunn]

We probably don't need the whole filepath.Clean(path). We should be fine, even if we just remove the ./ or .\.

[junegunn]

9b30ec5 removes filepath.Clean. It does not perfectly clean up fzf --walker-root ./././../././, but I don't care.

[junegunn]

Merged, thanks!