git remove from history

src: http://stackoverflow.com/questions/307828/git-remove-file-accidentally-added-to-the-repository

git filter-branch --index-filter 'git rm --cached --ignore-unmatch config/databases.yml' 38934e4182..HEAD

or

# create and check out a temporary branch at the location of the bad merge
git checkout -b tmpfix 

# remove the incorrectly added file
git rm somefile.orig

# commit the amended merge
git commit --amend

# go back to the master branch
git checkout master

# replant the master branch onto the corrected merge
git rebase tmpfix

# delete the temporary branch
git branch -d tmpfix