How to change gitignore on the fly?

Question

git

I have a folder that is ignored app/design/frontend/rwd/and all its contents are also ignored, I did a couple of times push.
But now I need to create a file there vendor.xmlthat should not be ignored.
Made so:
!app/design/frontend/rwd/vendor.xml
But it all the same is ignored! I do git statusbut it is not tracked and git add app/design/frontend/rwd/vendor.xmlalso tried!
What to do in such cases so that the git stops ignoring it?

Answer 1

Solved a problem:
git add -f app/design/frontend/rwd/vendor.xml

Answer 2

is it
stackoverflow.com/questions/987142/make-gitignore-...
?

Answer 3

git add app/design/frontend/rwd/vendor.xml