Do not unapprove if the update is a merge commit

[Balazs Szakmary]

This hook should be triggered only for "real" commits, not for merging e.g. master into a feature branch to make the PR mergeable.

[Balazs Szakmary]

All issues are untouched. If I implement this in a fork, will somebody review and merge my pull request?

[Balazs Szakmary]

Implemented this, created a pull request

[Julius Davies [bit-booster.com]]

PR-22 (to solve issue #15 and issue #14) will also solve this, and was merged today.

[Bryan Turner]

As @gsylviedavies has indicated, pull request #22 introduces a change which uses git patch-id to determine whether a rescope introduces changes to the effective diff. If it doesn't, approvals are no longer withdrawn.

That doesn't directly satisfy this issue--for example, pushing a merge which resolves conflicts is likely to update the diff and withdraw approvals--but it's about as close as we're likely to come. I think rather than just ignoring merge commits outright, evaluating whether the diff has changed is a better approach. Merges are just like any other commit in their ability to introduce changes, and so-called "evil" merges should still withdraw approvals.