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* Newer Debian packages install completions file in
/usr/share/doc/fzf/examples/completion.zsh

* Default to buster/stretch path if completion file not found

See file list in order from older to newer fzf package versions:
- https://packages.debian.org/stretch-backports/amd64/fzf/filelist
- https://packages.debian.org/buster/amd64/fzf/filelist
- https://packages.debian.org/bullseye/amd64/fzf/filelist
- https://packages.debian.org/sid/amd64/fzf/filelist

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

Typo introduced in f56b6788 fixing #8253

Fixes #8253
Co-authored-by: Mariusz B <mb@binary-offensive.com>

* fzf: Fix shell directory for archlinux package

* fzf: Don't clutter PATH if fzf already available

* brew has it available via symlink in /usr/local/bin
* Fedora and Arch packages have it place in /usr/bin

* fzf: Fix archlinux guess by using release file

* fzf: unset leftover variables