Preserve current directory in case current directory is changed by others
after the call of s:open

Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Close #2086

Nix can be installed on (almost) any Linux distro and on macOS.

See https://nixos.org/nix/ for more information.

Close #2081

Fix #2093

And we'll phase out height specification with `~` prefix.

Fix #2010
Fix #1638

Fix #2088

Vim 8.1.2371
https://github.com/vim/vim/commit/05ad5ff0ab34ed9a5296dedd420ca81698b8ce22

Nvim 0.4.0
https://github.com/neovim/neovim/commit/9a1675b065394734ddaef91a314896028e2b1d46

Fix #2087

If a user has the Powershell Community Extensions installed, it comes
with another command Expand-Archive that doesn't have a DestinationPath
argument, causing an error.

* Use --line-range instead of head in bat example

* README: extend preview section

When called with popup options, do not move to temp window.

The action takes place in the alternate screen so the offsets should
still be correct.

* No need to restore &wfw and &wfh when using popup window

Co-authored-by: lacygoill <lacygoill@lacygoill.me>
Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Fix #2038 

s///r is only available since perl 5.14. The Perl oneliner
was changed to work with older Perls, possibly even with 5.000.

Fix #2001

* Add RuboCop Minitest extension
* Improve error messages
* Use chomp option

Make sure that `extldflags` is quoted so that LDFLAGS containing spaces won't break the build command.

Close #1994

Close #1949

Support both ordinary completion trigger and empty trigger

    kill <tab>
    kill foo**<tab>

Close #1988
Close #385

Close #1986

Fix #1973
Fix #1974
Fix #1975

Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Since we don't know in advance which flags tmux will support, simply
allow a single uppercase character ([A-Z]) for now.

    fzf-tmux -xR -yS
    fzf-tmux -x R -y S

Fix #1956

e.g.

  if exists('$TMUX')
    let g:fzf_layout = { 'tmux': '-p90%,60%' }
  else
    let g:fzf_layout = { 'window': { 'width': 0.9, 'height': 0.6 } }
  endif

The following code works in zsh 5.8 but not in 5.4

  ${(Q)${(Z+n+)FZF_TMUX_OPTS:--d${FZF_TMUX_HEIGHT:-40%}}}