"git add" doesn't work in Power Shell

``` bash
C:\GitHub\github-for-developers-sept-2015 [master +0 ~2 -0]> git status
# On branch master
# Your branch is behind 'origin/master' by 27 commits, and can be fast-forwarded
.
# (use "git pull" to update your local branch)
#
# Changes not staged for commit:
# (use "git add ..." to update what will be committed)
# (use "git checkout -- ..." to discard changes in working directory)
#
# modified: README.md
# modified: another file
#
no changes added to commit (use "git add" and/or "git commit -a")
C:\GitHub\github-for-developers-sept-2015 [master +0 ~2 -0]> git add README.md
C:\GitHub\github-for-developers-sept-2015 [master +0 ~2 -0]> git add '.\Another
file'
C:\GitHub\github-for-developers-sept-2015 [master +0 ~2 -0]> git status
# On branch master
# Your branch is behind 'origin/master' by 27 commits, and can be fast-forwarded
.
# (use "git pull" to update your local branch)
#
# Changes not staged for commit:
# (use "git add ..." to update what will be committed)
# (use "git checkout -- ..." to discard changes in working directory)
#
# modified: README.md
# modified: another file
#
no changes added to commit (use "git add" and/or "git commit -a")
C:\GitHub\github-for-developers-sept-2015 [master +0 ~2 -0]>
```

Reproduce the commands in PowerShell with the modified README.md and the file named "another file", starting with git status and git add. Determine why neither file becomes staged and document or verify the expected staging behavior, including paths containing spaces.

Rédigé par le modèle d'indexation à partir du texte de l'issue.