If my understanding is correct, the purpose of the 'no more than 15 commits' heuristic is to try to ensure the branch has been rebased properly.

However, there is a better way to do that:

git merge-base master branch_name

will tell you which commit was the point where branch_name separated from master, and

git show -s --format=%ci `git merge-base master origin/MDL-43089`

will get you the date of that commit.

Verifying that

git log --oneline ^master origin/MDL-43089 | wc

gives the same output as

git log --oneline --no-merges ^master origin/MDL-43089 | wc

Will confirm that the branch is a simple branch.

Really, I just wanted CiBoT output for MDL-43089, to see where we were at.