Git escapes special characters in it's output when core.quotePath is
true or unset. Git always expects unquoted file paths as input. This
leads to issues when we consume output from git and use it to build
input for other git commands. This commit ensures we always feed unqoted
paths to git commands.
The _forgit_list_files function is introduced to handle usage of git
ls-files with the -z flag, which ensures unquoted paths.
It replaces the direct calls to git ls-files in _forgit_reset_head,
_forgit_stash_push and _forgit_checkout_file.
In _forgit_add the current approach of using colors to separate unstaged
from staged files is replaced with a call to _forgit_ls_files with the
appropriate flags to only list unstaged files.
In _git_reset_head the -z option is added to the git diff command to
ensure unqoted paths.
Since git clean does not support the -z flag, we disable core.quotePath
by passing a configuration parameter in _forgit_clean.

when the sed pattern matches (due to missing indicator)