comparing code on different branches

[Jean-Christophe Helary]

Sorry, it is more a git question than an emacs question:

I have created a branch where I do my work.

Now, when I test my code modifications, I do eval-buffer etc. But what if I 
also want to test what master does to compare the results?

Do I have to go through a stash/checkout/test/checkout stash apply cycle?

I thought I could actually do my modifications in the scratch buffer and keep 
the original file clean, so that I can always compare, but that seems a bit 
convoluted. Any better idea?

Jean-Christophe