Unfuddle STACK Tips & Tricks
How do I compare contents of a file in two different branches in my Git repository?
git-diff  you can compare contents of a file in between two branches.
# Changes between # the feature and the master branches $ git diff feature master -- myfile.txt # OR $ git diff feature..master -- myfile.txt
Notice the difference between two dots (..) and three dots (...) when comparing a file in between branches:
# Changes that happened on # the master branch since when # the feature branch was started from it $ git diff feature...master -- myfile.txt
You may also compare contents of different files in different branches by using a slightly different syntax:
# diff contents of myfile.txt # from the feature branch with # contents of yourfile.txt # from the master branch $ git diff feature:myfile.txt master:yourfile.txt
Check the Full Official Documentation for git-diff for more options.