Merging PR stacks mangles commit messages

[jstasiak]

I had a PR stack with one PR having this title: "Restrict upload routing to shipment dates", and this description:

There is some sentence here referring to [1] and saying something else.

[1] https://foo.bar.baz.slack.com/wat/archives/12312312312/12312312312312312

The full commit message (including the subject) of the only commit in that PR was:

Restrict upload routing to shipment dates

There is some sentence here referring to [1] and saying something else.

[1] https://foo.bar.baz.slack.com/wat/archives/12312312312/12312312312312312

When I used the squash merge method of merging the PR stack (one commit per PR in the target branch) the commit for the PR above was merged with this commit message:

Restrict upload routing to shipment dates

There is some sentence here referring to [1] and saying something else.

[1]
https://foo.bar.baz.slack.com/wat/archives/12312312312/12312312312312312