Windows: path separator issues

[konopka]

There are currently multiple open issues for this:
#646 , #254 , #393
And even some open PRs:
#591 , #618, #654

My issue comes from Telescope git_files and git status functions and path_display setting which is not working correctly.
Since git (and there may be other unix/linux utilities which do the same) ignores OS specific path separator and always uses '/'
path processing becomes i bit of a nightmare.

I'd like to propose that Path utils always normalize path separator in constructor to the path separator valid for current OS.
There might be problems with this approach where someone might expect unix like path even on windows ...
For those scenarios maybe a helper function would be appropriate which would return unix style path

Anyways, here is my dirty fix that solves MY issue with git in telescope

diff --git a/lua/plenary/path.lua b/lua/plenary/path.lua
index 0865f2e..b93e79e 100644
--- a/lua/plenary/path.lua
+++ b/lua/plenary/path.lua
@@ -261,6 +261,11 @@ function Path:new(...)
     path_string = table.concat(path_objs, sep)
   else
     assert(type(path_input) == "string", vim.inspect(path_input))
+       if path.sep == "\\" then
+               -- quickfix: on windows some utilities, e.g. git, return paths with '/' instead of '\'
+               -- so we will replace it here so that the rest of path processing works as expected
+               path_input = string.gsub(path_input, "/", "\\")
+       end
     path_string = path_input
   end