Add support for `undo`

[creack]

It would be nice to have an undo feature.

I don't know about bash, but zsh and emacs use <ctrl + _> for this and it is very very useful.

[Granjow]

FYI: Bash supports undo with Ctrl+_

[Granjow]

Just for clarification, it is not undoing a command (like, undo rm -f *), but undoing an edit command like delete word (Alt+d) or kill to EOL (Ctrl+k)?

[kenenbek]

Sorry, is still this feature unimplemented?

[faho]

Yes.

[kek]

I didn't know about the use case for undo in a command line, because if I would delete something by mistake with Ctrl-K, Ctrl-W or Ctrl-U, I would just use Ctrl-Y to paste it back. It seems to work in fish too. Could that be considered a workaround?

[adambyrtek]

I don't think it's just about line editing commands. I often use undo (in zsh) for cancelling the last Tab expansion that for some reason went too far (for example due to a typo).

[Ambrevar]

From http://fishshell.com/docs/current/index.html#editor:

u undoes the most recent action.

I guess that was a little too anticipated then... :p

[krader1961]

I guess that was a little too anticipated then.

Yes, that dates back to when vi mode was implemented with commit f68f91b on 2014-11-08. Obviously it was a bit of wishful thinking. I've removed that line from the docs. At the moment it is bound to history-search-backward.