Skip double CI build on main branch pull requests (#1491)
Skip double CI build on main branch pull requests (#1491)

Why:
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The trigger for the build job is either a `push` or a `pull_request`.
When a pull request is opened against master two CI run start, since
both triggers are valid.

This Commit:
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- Skip the build job if the event is a pull request made from the same
repository. Since a CI build job hast started already because a push
trigger was detected.
thoughtbot/factory_girl