Learn from Remove files from Git commit

I am learning to use git to manage my project.

Once I need to add many files, so I directly use git add -a to add all of them. But I added one file whose filesize is larger than 100M. When I push my commit, it shows File XXX is 190 MB; this exceeds github's file size limit of 100 MB.

Please refer to Conditions for large files.

What I want to do is to remove such big files from the last commit.

1.revert to HEAD^

git reset --soft HEAD^

or

git reset --soft HEAD~1

2.reset the unwanted files in order to leave them out from the commit:

git reset HEAD path/to/unwanted_file

3.commit again, you can even re-use the same commit message:

git commit -c ORIG_HEAD