Use plenary.job to fix .git detection on windows, add regex fix for renamed files

[cjgibbons]

Multiple fixes for issues are contained in this PR:

• This PR fixes Issue #954 by changing:

  • the call to vim.fn.system() with plenary.job, and then testing the return value after the job finishes.
  • the call to git_root_of_cwd() with plenary.job, testing the return value and if in error defaults to vim.fn.getcwd() otherwise returns the directory from git rev-parse --show-toplevel

  On Windows, the vim.fn.system() was returning 127, instead of the expected 0, resulting in false whenever is_inside_worktree() is invoked. In turn, this always means the prompt for initializing the git repos is displayed for every Neogit operation. Plenary.job produces a 0 on success.

  Similarly, the call to git_root_of_cwd() kept returning the empty string "" (due to the non-zero success values) so vim.fn.getcwd() was always being called. The above change reduces the abstraction by making opts.cwd have either the git toplevel directory or the current working directory whenever git_root_of_cwd() is invoked.

• This PR also fixes Issue #1256:

  • By matching on the beginning of the line and looking for 2 R only then the regex matches the case for renamed files AND renamed and staged files. Since the file paths are matched properly they can be edited normally.

[AddictArts]

+1 When time permits. I am on Window, so important to me. Is there something holding this up @CKolkey

[CKolkey]

Good stuff! I don't have a windows installation, so I appreciate the assistance in ensuring a smooth experience with the platform :)

[AddictArts]

Thanks, awesome and appreciated.