How do I see the commit differences between branches in git?

You can easily do that with

git log master..branch-X

That will show you commits that branch-X has but master doesn't.

You can get a really nice, visual output of how your branches differ with this

git log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr)%Creset' --abbrev-commit --date=relative master..branch-X

I think it is matter of choice and context.I prefer to use

git log origin/master..origin/develop --oneline --no-merges

It will display commits in develop which are not in master branch.

If you want to see which files are actually modified use

git diff --stat origin/master..origin/develop --no-merges

If you don't specify arguments it will display the full diff.If you want to see visual diff, install meld on linux, or WinMerge on windows. Make sure they are the default difftools .Then use something like

git difftool -y origin/master..origin/develop --no-merges

In case you want to compare it with current branch. It is more convenient to use HEAD instead of branch name like use:

git fetchgit log origin/master..HEAD --oneline --no-merges

It will show you all the commits, about to be merged