New users (especially ones unfamiliar with CLI programs) intuitively
expect `jj undo` to work the same way the "undo" functionality of
typical GUI applications do. That means, running `jj undo` multiple
times should restore progressively older states of the repository
one-by-one.
Related feature request "jj undo ergonomics":
https://github.com/jj-vcs/jj/issues/3700
This paves the way for the semantics of `jj undo` and `jj op revert` to
evolve independently. `jj op revert` is going to stay the low-level
command to apply the inverse of any operation. The new name is
consistent with `jj revert`, which applies the inverse of a commit.
`jj undo` on the other hand is planned to become a higher-level command,
which is more similar to, say, Ctrl+Z in typical GUI applications.
Running `jj undo` repeatedly will revert progressively older operations,
allowing the user to walk backwards in time. At the same time, `jj undo`
will lose the abilitly to revert arbitrary operations, to keep its
semantics simple and intuitive.
Related feature request "jj undo ergonomics":
https://github.com/jj-vcs/jj/issues/3700
"Concurrent" operations are not necessarily actually concurrent, so
"divergent" seems like a better name. And "reconcile" seems like a
better term for merging them, though we also sometimes use "merge".
A possible use case is when doing some archaeology around a certain operation.
The current implementation is quadratic if + is repeated. Suppose op_id is
usually close to the current op heads, I think it'll practically work better
than building a reverse lookup table.
