Fixes T4767. I believe 80% of this was actually caused by the author issue fixed in T5771, but this should help make the other 20% debuggable.

• Record why we didn't autoclose a commit when we process it.
• Show branch autoclose status in the main branch table.
• Show commit autoclose status on the edit screen.
• Add documentation about how to find these statuses and what they mean.

• Read documentation.
• Viewed branches and hovered over the various states.
• Viewed commits in various states and checked the "Autoclose?" field.
• Pushed some commits and saw autoclose activate.