Changelog diff urls customization

[oljekechoro]

Issue type

• bug report
• idea
• question
• other

Expected behavior

User sets a template string for diff urls in changelogs. The template string accepts some vars to form url.

Actual behavior

There is no ability to change diff urls in changelogs.

• I've read the docs. This case is not mentioned
• Similar issue does not exist

[oljekechoro]

tagDiffUrl: https://gerrit.foo.com/plugins/gitiles/${repoName}/+/refs/tags/${newTag}
commitDiffUrl: https://gerrit.foo.com/plugins/gitiles/${repoName}/+/${hash}%5E%21