Github: comparing across forks?

Question

Short version

When I compare two forks on Github, it does not compare the latest states, but the current state of the base fork with the last common com

Answer 1

https://github.com/github/linguist/compare/master...gjtorikian:master

github:master is up to date with all commits from gjtorikian:master.
Try switching the base for your comparison.

It means that all commits from gjtorikian/liguist are part of github/linguist.

The reverse is not true:
https://github.com/gjtorikian/linguist/compare/master...github:master

That would give all (1866) commits from github/linguist which are not part of gjtorikian/linkguist.

This is triple-dot '...' diff between the common ancestor of two branches and the second branch (see "What are the differences between double-dot “..” and triple-dot “…” in Git diff commit ranges?"):

In the first case github/linguist:master...gjtorikian/linguist:master, the common ancestor and gjtorikian/linguist:master are the same! O commits.

In the second case gjtorikian/linguist:master...github/linguist:master, github/linguist:master has 1866 commits since the common ancestor (here, since gjtorikian/linguist:master).