This form of git diff
just takes two revision specifiers, as described in gitrevisions.
In this case origin
is most likely to match item 6:
- otherwise,
refs/remotes/<refname>/HEAD
if it exists.
So this means the same as git diff origin/HEAD master
: resolve origin/HEAD
to a commit-ID, resolve master
to a commit-ID, and diff the two commits.
Run:
git rev-parse origin
to see how the resolution works.