Understanding diff against current ?

Question

I have two branches in source tree - master and branch-1. The current branch is master (in bold text in source tree). I right click on branch-1 and do "diff against current". Does this mean "git diff master branch-1", OR "git diff branch-1 master" ?

I wanted to merge branch-1 into master. But, before merging I want to see the changes which branch-1 would introduce into master. Should I select master as current & then then diff against branch-1 or vice versa ?

As an aside, is there a way to see all the commands which source tree performs in the background ? Thanks.

Mikael Sandberg · Answer

The command git diff master...branch will show all changes made in branch that have not yet been merged into master, same as compare against current in Sourcetree assuming branch is your current branch.

Borat Sagdiyev · Answer

@Mikael Sandberg- Sorry your previous comment is not clear.
"My example assumes branch is the current branch." Which branch are you talking about after "assumes branch ???..."

Mikael Sandberg · Answer

Sorry, should have added that. My example assumes branch is the current branch.