In fish, I have an abbreviation that automatically expands double dots into ../ so that you can just spam double dots and visually see how far you're going.

  # Modified from
  # https://github.com/fish-shell/fish-shell/issues/1891#issuecomment-451961517
  function append-slash-to-double-dot -d 'expand .. to ../'
   # Get commandline up to cursor
   set -l cmd (commandline --cut-at-cursor)
  
   # Match last line
   switch $cmd[-1]
   case '*.'
    commandline --insert './'
   case '*'
    commandline --insert '.'
   end
  end

I used to do this, but unary kind of sucks after 3; So maybe others might like this better before their fingers get trained:

    ..() { # Usage: .. [N=1] -> cd up N levels
      local d="" i
      for ((i = 0; i < ${1:-"1"}; i++))
        d="$d/.."  # Build up a string & do 1 cd to preserve dirstack
      [[ -z $d ]] || cd ./$d
    }

Of course, what I actually have been doing since the early 90s is realize that a single "." with no-args is normally illegal and people "cd" soooo much more often than sourcing script definitions. So, I hijack that to save one "." in the first 3 cases and then take a number for the general case.

    # dash allows non-AlphaNumeric alias but not function names; POSIX is silent.
    cd1 () { if [ $# -eq 0 ]; then cd ..; else command . "$@"; fi; } # nice "cd .."
    alias .=cd1
    cdu() {           # Usage: cdu [N=2] -> cd up N levels
      local i=0 d=""  # "." already does 1 level
      while [ $i -lt ${1:-"2"} ]; do d=$d/..; i=$((i+1)); done
      [ -z "$d" ] || cd ./$d; }
    alias ..=cdu
    alias ...='cd ../../..' # so, "."=1up, ".."=2up, "..."=3up, ".. N"=Nup

and as per the comment this even works in lowly dash, but needs a slight workaround. bash can just do a .() and ..() shell function as with the zsh.

I need this *so* often that I programmed my shell to execute 'cd ..' every time I press KP/ i.e. '/' on the keypad, without having to hit Return.

Other single-key bindings I use often are:

KP* executes 'ls'

KP- executes 'cd -'

KP+ executes 'make -j `nproc`'

How? Readline macros?

Literally with my own shell: https://github.com/cosmos72/schemesh

up() { local d="" for ((i=1; i<=$1; i++)); do d="../$d" done cd "$d" }

up 2, up 3 etc.

fish lets you cd to a folder without 'cd' although you still need the slashes. I use it all the time.

    c $> pwd
    /a/b/c
    c $> dir1
    dir1 $> ..
    c $> ../..
    / $>

zsh also does, with `setopt autocd` https://zsh.sourceforge.io/Intro/intro_16.html

I have setup a shortcut: alt+. to run cd.., it's pretty cool.

I also aliased - to run cd -

but alt-. in bash is used for pasting the last argument to the previous command into the current one.

Good point, when working with keybindings, you'll inevitably end up overriding built-ins. I see it as a trade-off, between something I don't know of (and wouldn't use) and something I find useful. Works for me :)

absolutely. From back in the day, the annoying one was GNU screen, which took over ctrl-a by default. Overrode that to be ctrl-^, which in bash is transpose, make "zx be "xz", which was rare enough to okay with losing.

it was ctrl-t, not ctrl-^

Does zsh support this out-of-the-box? Because I definitely never had to setup any of these kinds of aliases but have been using this shorthand dot notation for years.

It's an oh-my-zsh thing.

Yes it does.

Not on my Mac.

    zsh: permission denied: ..
    zsh: command not found: ...

alias cdtop=’cd $(git rev-parse --show-toplevel)’