My current fish prompt. Shows the current directory, who's logged in, current host (last two helpful for SSH sessions) and then a git status prompt displaying current branch and the branches status. Finally the actual prompt is on the next line, to keep lots of space for commands.

fish_prompt.fish

set -g __fish_git_prompt_show_informative_status 1
set -g __fish_git_prompt_hide_untrackedfiles 1

set -g __fish_git_prompt_color_branch magenta bold
set -g __fish_git_prompt_showupstream "informative"
set -g __fish_git_prompt_char_upstream_ahead "↑"
set -g __fish_git_prompt_char_upstream_behind "↓"
set -g __fish_git_prompt_char_upstream_prefix ""

set -g __fish_git_prompt_char_stagedstate "●"
set -g __fish_git_prompt_char_dirtystate "✚"
set -g __fish_git_prompt_char_untrackedfiles "…"
set -g __fish_git_prompt_char_conflictedstate "✖"
set -g __fish_git_prompt_char_cleanstate "✔"

set -g __fish_git_prompt_color_dirtystate blue
set -g __fish_git_prompt_color_stagedstate yellow
set -g __fish_git_prompt_color_invalidstate red
set -g __fish_git_prompt_color_untrackedfiles $fish_color_normal
set -g __fish_git_prompt_color_cleanstate green bold

set -g user (whoami)
set -g host (hostname)


function fish_prompt --description 'Write out the prompt'

  set -l last_status $status

  if not set -q __fish_prompt_normal
    set -g __fish_prompt_normal (set_color normal)
  end

  # PWD
  set_color $fish_color_cwd
  printf "[%s] " (prompt_pwd)
  set_color normal

  printf "$user@$host %s " (__fish_git_prompt)

  if not test $last_status -eq 0
  set_color $fish_color_error
  end

  echo -n -e '\n$ '

end