Untrack A File Without Deleting It
Generally when I invoke git rm <filename>, I do so with the intention of
removing a file from the project entirely. git-rm does exactly that,
removing the file both from the index and from the working tree.
If you want to untrack a file (remove it from the index), but still have it
available locally (in the working tree), then you are going to want to use
the --cached flag.
$ git rm --cached <filename>
If you do this, you may also consider adding that file to the .gitignore
file.