Should a changelog link to Issues or PullRequests?

[buhtz]

Should an entry (e.g. "Fix") in a changelog link to the bug report or to the pull request closing this bug? Is there a convention or good reasons for one or the other?

I can't decide myself.

There is also an ongoing discussion on reddit: https://www.reddit.com/r/opensource/comments/1apveiq/should_a_changelog_link_to_issues_or_pullrequests/?utm_source=share&utm_medium=web2x&context=3