FR: jj undo ergonomics

[benbrittain]

Is your feature request related to a problem? Please describe.
The current behavior of the jj undo command does not seem to be what users intuitively expect. Currently if you run jj undo twice in a row it has the same behavior as jj op undo, it returns you to the same place you were when you started. undo + undo = no change.

Describe the solution you'd like
I'd like to preserve the ergonomics of the underlying jj op undo command (as suggested by @PhilipMetzger on Discord), but have the higher level jj undo command track if a user immediately undoes an undo and warn them.

Describe alternatives you've considered
Alternatively, the jj undo command could keep track of where you are in the undo log ctrl-Z style. That probably implies a redo command as well?

[martinvonz]

I'd like to preserve the ergonomics of the underlying jj op undo command

Why make them different? Oh, I suppose the top-level jj undo would lose its optional operation argument?

[benbrittain]

I'm actually starting to question if jj op undo is needed at all. I'd originally been modeling it as a lower level operation, but it's really just a special case of jj op restore, no? I can't imagine I'd ever use jj op undo if jj undo had ctrl-z semantics

[martinvonz]

it's really just a special case of jj op restore, no?

No, jj undo @- undoes the second-to-last operation while leaving the changes from the last operation. For example, if you abandoned some commit, and then did a bunch of unrelated changes, you can still recover that commit with jj undo <old operation>. It can be hard to reason about, however, because it also brings back ancestors of the old commit when it makes the old abandoned commit visible.

[martinvonz]

Think of it like jj backout but for operations (while jj op restore is jj restore for operations).

[PhilipMetzger]

To reword the FR a bit:

Improve the ergonomics of jj undo by making it a separate command, which can do undo tracking like editors. Currently running undo twice in a row, surprises a lot of users as it just rolls back the last operation (not surprising if you know that jj undo is an alias of jj op undo). This would then pave a way for a smart redo, which has the opposite behavior.

Describe alternatives you've considered
Alternatively, the jj undo command could keep track of where you are in the undo log ctrl-Z style. That probably implies a redo command as well?

I think that this alternative would be layering violation in UI terms, as imo jj op undo shouldn't be aware of such things anyway. That's where the suggestion came from in Discord anyway.

[joyously]

Would this have any impact on #3428 (op log waypoints)?

[PhilipMetzger]

Would this have any impact on #3428 (op log waypoints)?

The higher level jj undo could probably integrate with them, which then simplifies the UX again. op log Waypoints will just be another nice building block for it.