try git commit -a -m '[your commit message]'
edit: git need always a comment for each commit, you can by the way add an empty comment with
git commit -a -m ''
or
git commit -am ''
Committing with a message is necessary when using Git, but is also helpful:
Crafting the commit message is a very important step of your development work. The message is usually the first thing other developers will see, and the first line in a Git commit-msg has a special meaning. It is considered the "Title" or "Subject" of the commit. Many interfaces use this title to represent the commit, such as:
-Subject of e-mail notifications
-git log's "oneline" mode
-Gerrit interface (dashboard, search results, title)
-Git revert (cites the commit title)
-Various Git GUI clients
(use first line as title until first empty line or end of body)