more FAQ material

[joyously]

I saw a reference to https://dangitgit.com/ and wondered if jj adequately answers all of these issues. Perhaps the jj answers could be part of the FAQ or other docs?

• I did something terribly wrong, please tell me jj has a magic time machine!?!
• I need to make one small change!
• I need to change the message on my last commit!
• I committed something to master that should have been on a brand new branch!
• I accidentally committed to the wrong branch!
• I tried to run a diff but nothing happened?! (maybe not applicable to jj)
• I need to undo an old commit!
• I need to undo my changes to a file!
• Forget this noise, I give up.