The Pretested Integration plugin uses 'Branch Specifier' from the Git plugin as source branch, and 'Integration branch' field in the Pretested Integration plugin as destination.

When the integration job uses polling, the job only runs on branches that matches the "Branch Specifier", so only those are integrated.

When job is started in another way, eg. by upstream job with at Git commit SHA passed, it may try to integrate other branches (the one the passed git commit SHA lives on).

This is because the SHA is not translated to a branch, and that branch is checked against our criterias for running integration.

Translate SHA to branch name, and check that the conditions for running is okay (these conditions are established already, or in other cases).
Just implement translation.

See also JENKINS-24909