Branch difference in Gitlab

I want to show the branch differences of the GitLab. So I used https://docs.gitlab.com/ee/api/repositories.html#compare-branches-tags-or-commits

I did not understand how it is comparing the branches.

GET /projects/:id/repository/compare?from=master&to=feature in the above, what compares between master and feature?

Does this compare differences in terms of commits that are not available in master? Or shows different commits which are not available in each other?

As I observed it is showing the only differences that are not present in main.

If yes, how can I show the differences between both branches in using a single API?

Solution

Does this compare differences in terms of commits that are not available in master? or shows different commits which are not available in each other?

Your API call is missing the straight argument:

straight boolean: Comparison method.

true for direct comparison between from and to (from...to),

false to compare using merge base (from..to).

Default is false.

In your case, &straight=true would show you what you want.