Allow walking multiple root directories

[msabathier]

Hi,
I have been trying to search a file or directory with fzf on Windows on multiple drives.
I managed to do it by piping the output of Get-ChildItem cmdlet (slow) and then the output of fd (faster but not ideal).
It was not a satisfying solution to me so i started to look at the code of fzf and found a solution to this problem by using a comma separated list in the --walker-root argument.
I am not proficient in go so the implementation might not be what you are looking for, don't hesitate to guide me towards a solution that suits you.
Best regards,
Martin

[junegunn]

then the output of fd (faster but not ideal)

Can you explain why it felt not ideal? fd is a dedicated directory traversal program with much more versatility (notably .gitignore support). The built-in walker of fzf can be a good default for many users, but it isn't supposed to be, or tries to be, as good as dedicated external programs.

[msabathier]

That was also my initial thought, but after a bit of testing, I found that the built-in walker was actually quite faster than fd, at least on Windows (maybe the piping is introducing some overhead ?).

Also when using fd, the pipe crashes if I select a result before fd has finished executing. This can probably be fixed but it led me to test other solutions first, one of which was this PR that I found was faster and more practical than using fd.

[junegunn]

/cc @charlievieth FYI