Find commit that first added a particular line of code on Github

First, you have to clone the repository to your machine:

git clone https://github.com/BVLC/caffe.git

Simply use git-blame to find out who committed a certain line:

git blame -L 123,123 path/to/file.cpp

Or, for a range of lines, use -L 100,150 or similar. You may want the option -M which detects if lines were moved.

You can also use git-log for the entire commit log:

git log -L 123,123:path/to/file.cpp