Support windows path and env

[yehuohan]

• Add windows path (works for cmdline too): x:\foo\bar, x:/foo\bar
• Add brace-env path (not for cmdline, convenient for bash coding): ${HOME}/, ${HOME}\
• Add windows env path (not for cmdline): %HOME%/, %HOME%\

[waldimen]

I hope this will be merged, I checkout this commit, and it works find on my windows machine and it is very useful.

[pidgeon777]

Is it possible to adapt it to also support relative paths? (relative to neovim pwd).

[yehuohan]

Is it possible to adapt it to also support relative paths? (relative to neovim pwd).

You mean provide completion items for ./?

[pidgeon777]

Yes, let's assume that :pwd in Neovim returns:

C:\path\to\dir

And this dir contains:

file1
file2
subdir\file1
subdir\file2

Then, I expect that when typing in insert mode:

.\

and activating the nvim-cmp popup, the possible autocomplete choices should include:

.\file1
.\file2
.\subdir\file1
.\subdir\file2

...or perhaps it would be better if, after triggering with .\, the nvim-cmp popup directly showed:

file1
file2
subdir\file1
subdir\file2

without prefixing each file with .\? This, of course, is specifically for Windows.

However, I believe that solution "1" (including the .\ before each file) is the most "consistent".

[yehuohan]

Think your detailed description. This PR supports .\ and I'm sure I can get completions from both ./ and .\