Diff Previews when linking a PR

[oceanseth]

Checklist

• This is a new feature, not a refactoring suggestion
• I have checked for this feature in the Sourcery documentation
• I have checked there are no open requests referencing the same feature

Description

When linking a PR to another developer, the preview that gets shown is something like

This pr has a VERY small change, and seeing something like

would be much more useful.

detecting how to provide GOOD previews, generating images for open graph image previews would be something sourcery could do well that would provide a lot of value!

[brendanator]

Hi @oceanseth, this is GitHub functionality rather than Sourcery functionality. Unfortunately we cannot output the diff in the preview as it comes directly from the PR title and body