Q:

How to find diff in a specific file on git using web browser

I know for Git Bash, you can use this command:git diff [--options]   [--] [...] but I want to know if there is any way to find difference between a specific file using browser. 
Like we can find changes in commits, but that includes all files (https://github.com/github/linguist/compare/c3a414e..faf7c6)
I just want to find changes to one specific file.

A:

You can at least (through the browser) see commits which actually involved a given file.
For that, you need to access the "History" page of said file:
https://github.com/github/linguist/commits/master/lib/linguist/heuristics.rb
But that does not give you any diff between two commits.
Another workaround is at least to get to the blame view of that file.
https://github.com/github/linguist/blame/master/lib/linguist/heuristics.rb
For any diff shown here, you can click and see the previous revision information for that line, including who committed the change and when. 

