Close #1874

e.g.

  let g:fzf_layout = { 'window': { 'width': 0.4, 'height': 1, 'xoffset': 0, 'border': 'right' } }
  let g:fzf_layout = { 'window': { 'width': 0.4, 'height': 1, 'xoffset': 1, 'border': 'left' } }
  let g:fzf_layout = { 'window': { 'width': 1, 'height': 0.5, 'yoffset': 1, 'border': 'top' } }
  let g:fzf_layout = { 'window': { 'width': 1, 'height': 0.5, 'yoffset': 0, 'border': 'bottom' } }

Revert the change introduced in #552. It seems that the startup time
difference between bash and fish is not much of an issue now.

  > time bash -c 'date'
  Thu Feb 13 21:15:03 KST 2020

  real    0m0.008s
  user    0m0.003s
  sys     0m0.003s

  > time fish -c 'date'
  Thu Feb 13 21:15:05 KST 2020

  real    0m0.014s
  user    0m0.007s
  sys     0m0.006s

When we explicitly *pipe* $FZF_DEFAULT_COMMAND instead of making fzf
internally start the process ($FZF_DEFAULT_COMMAND | fzf), fzf may hang
if the input process doesn't quickly process SIGPIPE and abort.

Also, fzf#vim#grep temporarily swaps $FZF_DEFAULT_COMMAND instead of
setting 'sink' so fzf can kill the default command on 'reload'.

https://github.com/junegunn/fzf.vim/issues/927

However, because of the "pipe conversion", the trick wasn't working as
expected.

https://github.com/junegunn/fzf.vim/blob/467c3277884240f7b5430f8f4d600e3415c38f3b/autoload/fzf/vim.vim#L720-L726

We can go even further and always set $FZF_DEFAULT_COMMAND instead of
piping source command.

Credits to @jiangjianshan

Close #1856
Close #1857

Close https://github.com/junegunn/fzf.vim/issues/942

e.g.
  let g:fzf_layout = { 'window': { 'width': 0.9, 'height': 0.6 } }

Based on the code from https://github.com/junegunn/fzf.vim/issues/821#issuecomment-581273191
by @lacygoill.

Truecolor does not work on default Windows terminal.
It is a problem in neovim GUIs.

https://github.com/sainnhe/edge/issues/5#issuecomment-565748240

* Add MSYS2 support as a vim plugin

Add &shellcmdflag and TERM environment variable treatment.

- Make &shellcmdflag `/C` when &shell turns into `cmd.exe`
- Delete %TERM% environment variable before fzf execution

* Change shellescape default value depending on s:is_win flag

* Make TERM environment empty only when gui is running

* Stop checking &shell in fzf#shellescape function

This funcion's behavior is controlled by only if it is Windows or not.
So there is no need to check &shell.

* Take neovim into consideration when to set shellcmdflag

* Add &shellxquote control

Backport https://github.com/junegunn/vim-plug/pull/913

In recent Nvim versions, an "Error running ..." message is shown even for normal
use cases, such as:

    :Files
    <c-\><c-n>
    :close

Closing the window will :bwipeout! the terminal buffer, because fzf sets
bufhiden=wipe.

When deleting the terminal buffer while fzf is still running, Nvim sends SIGHUP.
This happens for quite some time already, but the bug only manifests since this
commit:

  https://github.com/neovim/neovim/commit/939d9053b

It's The Right Thing to do when the application exited due to a signal.

Before that commit, no "Error running ..." message was shown, because 1 (instead
of 128 + 1 == SIGHUP) was returned which the exit handler in fzf.vim treats as
"NO MATCH".

https://github.com/junegunn/vim-plug/pull/891

https://github.com/junegunn/vim-plug/pull/888

By @gh4w and @janlazo

See https://github.com/junegunn/vim-plug/commit/68b31a4a66ec945ff299db25a8a6382cd48edf14

Fix https://github.com/junegunn/fzf.vim/issues/855

(i.e. spawn xterm)

Close #1539

Close #1535

Close #1356

Related:
- #612
- https://github.com/junegunn/fzf.vim/issues/308

Close #1085
Close #1086
Close https://github.com/junegunn/fzf.vim/issues/678

Close #1288

Close #1268

Fix #1205

Close #1172

The issue is fixed in https://github.com/vim/vim/commit/1232624ae5b56c167c5982a2620f736c4bbc19ef

Close #1152

msys2 terminal Vim assumes that it runs in mintty
so `:terminal` uses `TERM=xterm`.
fzf doesn't support `TERM=xterm` on Windows.

Close #1066
Close #1068

Close #1055

Prevents the following case:
before pathshorten - /usr/bin
after pathshorten - /u/bin
piped to cmd.exe - U:/bin

Port of https://github.com/junegunn/fzf.vim/commit/e7928d154aad71e530daf5c17733275da5732680

Since :FZF does not enable preview window, we determine based on full
&columns instead of &columns / 2.

Temporary workaround for non-Windows environment

Reference:
https://github.com/vim/vim/issues/1998
https://github.com/junegunn/fzf/pull/1019#issuecomment-327008348

IMPORTANT:
cmd.exe and powershell are fine in default Windows terminal.
cmd.exe prompt is broken on ConEmu because it natively supports ucs-2 only.
utf-16 support is exclusive to .Net (ie. powershell).
utf-8 supports requires chcp, external program, but does not fix the cmd.exe prompt.
Use powershell on ConEmu to avoid corrupted text on display

Requirements:
- compiled with +terminal
- has patch-8.0.995
- has('gui_running') returns 1