git push says everything up-to-date even though I have local changes

Question

I have a remote gitosis server and a local git repository, and each time I make a big change in my code, I'll push the changes to that server too.

But today I find that even though I have some local changes and commit to local repository, when running git push origin master it says 'Everything up-to-date', but when I use git clone to checkout files on the remote server, it doesn't contain lastest changes. And I have only one branch named master and one remote server named origin.

PS: This is what git displays when running ls-remote, I'm not sure whether it helps

$ git ls-remote origin
df80d0c64b8e2c160d3d9b106b30aee9540b6ece        HEAD
df80d0c64b8e2c160d3d9b106b30aee9540b6ece        refs/heads/master
$ git ls-remote .
49c2cb46b9e798247898afdb079e76e40c9f77ea        HEAD
df80d0c64b8e2c160d3d9b106b30aee9540b6ece        refs/heads/master
df80d0c64b8e2c160d3d9b106b30aee9540b6ece        refs/remotes/origin/master
3a04c3ea9b81252b0626b760f0a7766b81652c0c        refs/tags/stage3