Is there a context for this change?
There is some context on Meta:
Thanks. I’m going to ask someone who is more familiar with email than me to check this out!
Why the need to (re)set it to
nil when you are going to set it to either a value or
nil on the next line?
Before I added the line, the same header was added twice, with the old and new value.
Right, then I think this behavior is worth adding a comment.
This pull request has been mentioned on Discourse Meta. There might be relevant details there: