Fish like up/down history/buffer navigation in Zsh

smart-up-and-down.zsh

# 0 = history mode, 1 = edit mode
typeset -g __editing=0

# Up: history until editing begins
function smart-up() {
  if (( __editing )); then
    zle up-line-or-history
  else
    zle up-history
  fi
}
zle -N smart-up

# Down: history until editing begins
function smart-down() {
  if (( __editing )); then
    zle down-line-or-history
  else
    zle down-history
  fi
}
zle -N smart-down

# Reset state when command is accepted
function accept-line() {
  __editing=0
  zle .accept-line
}
zle -N accept-line

# Mark editing on any non-history action
function __mark_editing() {
  __editing=1
  zle .${WIDGET}
}

# Any normal editing widget flips the mode
for w in self-insert backward-char forward-char \
         beginning-of-line end-of-line delete-char
do
  zle -N $w __mark_editing
done

# Bind smart up and down
bindkey "${terminfo[kcuu1]}" smart-up
bindkey "${terminfo[kcud1]}" smart-down