My personal fish shell config for OS X. Supports git branch (fast git checks), virtualenv (if installed) and Kubernetes current context

config.fish

function ls --description 'List contents of directory'
  command ls -lFG $argv
end

function subl --description 'Launches sublime text in a new window'
  command subl -n $argv
end

function code --description 'Launches visual code studio in a new window'
  command code -n $argv
end

function grep --description 'Colorful grep that ignores binary file and outputs line number'
  command grep --color=always -I $argv
end

function gf --description 'Do a git fetch'
  git fetch
end

function gdeletemergedcurrent --wraps git --description 'Delete all local branches that is already merged to current branch (excludes master and main)'
  git branch --merged | grep -v "\*" | grep -v "master" | grip -v "main" | xargs -n 1 git branch -d
  git remote prune origin
end

set -gx GOPATH $HOME/Go
set -gx GOROOT (go env GOROOT)
set PATH $HOME/bin $GOPATH/bin $HOME/.rbenv/shims /usr/local/bin /usr/local/sbin $PATH $GOROOT/bin ./node_modules/.bin

. $HOME/.config/fish/prompt.fish

# set -gx HOMEBREW_GITHUB_API_TOKEN #token here#

# Java
set -gx JAVA_HOME (/usr/libexec/java_home)

# Allow 256 colors in iTerm2 for pretty vim colors
set -gx CLICOLOR 1
set -gx TERM xterm-256color

prompt.fish

# use custom function instead of fish built in git prompt due to performance
# (fish git prompt uses diff which can be slow)
function git_prompt
  set -l git_status_origin (command git status -s -b 2> /dev/null)
  printf ''

  set -l is_repo (string join0 $git_status_origin)

  if test -z $is_repo
    # git status returns error (not a git repo)
    printf ''
  else 
    echo $git_status_origin | string match --regex '\[.*ahead.*\]' --quiet
    set -l ahead $status
    echo $git_status_origin | string match --regex '\[.*behind.*\]' --quiet
    set -l behind $status
    set -l branch (echo $git_status_origin | string replace -r  '## ([\S]+).*' '$1' | string replace -r '(.+)\.\.\..*' '$1')

    # simply check for modified/deleted/rename, match only 1
    echo $git_status_origin | string match --regex '[MDR ][MDR ] .*' --quiet
    set -l git_dirty $status

    # simply check for ?? in the list of files, match only 1
    echo $git_status_origin | string match --regex '\?\? .*' --quiet
    set -l git_untracked $status

    if test "$git_dirty" -eq 0
      printf ' (%s%s' (set_color red)
    else
      printf ' (%s%s' (set_color yellow)
    end

    # Use branch name if available
    if test -n "$branch"
      printf $branch
    else 
      # for new branch, git branch will return nothing, use branch name from git status
      set -l git_status_no_commits_branch (echo $git_status_origin | string replace '## No commits yet on ' '')
      printf $git_status_no_commits_branch
    end

    if test "$git_untracked" -eq 0
      printf '%s*' (set_color purple)
    end

    if test -s .git/refs/stash # stash exists - check on .git/refs/stash file
      printf '%s$' (set_color green)
    end

    # if local repo is ahead, show up arrow
    if test "$ahead" -eq 0
      printf '%s↑' (set_color cyan)
    end

    # if local repo is behind, show down arrow
    if test "$behind" -eq 0
      printf '%s↓' (set_color magenta)
    end
    printf '%s)' (set_color normal)
  end
end

function kubectl_context
  if test -e ~/.kube/config; and type -q kubectl
    set -l current_context (kubectl config current-context)
    printf ' %s[' (set_color normal) 
    printf '%s%s' (set_color cyan) $current_context
    printf '%s]' (set_color normal)
  else
    printf ''
  end
end

function fish_prompt
  # check for iterm2 shell integration
  if test -e {$HOME}/.iterm2_shell_integration.fish ; and source {$HOME}/.iterm2_shell_integration.fish
    printf ' '
  end
  
  printf '%s%s%s' (set_color $fish_color_cwd) (prompt_pwd) (set_color normal)
  printf '%s%s ☕️ ' (git_prompt) (kubectl_context)
  set_color normal
end

updated to remove all grep calls and use fish' built in string matcher which is faster than grep. Now the bottleneck is only on git status

~/w/demo (6.1.1-post*↓) ☕️ fish --profile /tmp/profile -c fish_prompt; sort -nk1 /tmp/profile | tail -n 10
72	72	----> echo $git_status_origin | string match --regex '\[.*ahead.*\]' --quiet
86	118	---> set -l is_repo (string join0 $git_status_origin)
87	87	--> set_color $fish_color_cwd
112	102796	---> set -l git_status_origin (command git status -s -b 2> /dev/null)
131	131	----> string replace -r '^'"$realhome"'($|/)' '~$1' $PWD
135	712	--> prompt_pwd
198	104113	-> printf '%s%s ☕️ ' (git_prompt) (kubectl_context)
233	246	---> source /usr/local/Cellar/fish/3.3.1/share/fish/functions/prompt_pwd.fish
265	1082	-> printf '%s%s%s' (set_color $fish_color_cwd) (prompt_pwd) (set_color normal)
102684	102684	----> command git status -s -b 2> /dev/null

upgraded to latest git and it's even faster now

~/w/demo (6.1.1-post*↓) ☕️  fish --profile /tmp/profile-oldgit -c fish_prompt; sort -nk2 /tmp/profile-oldgit | tail -n 10
64        200     ---> set -l tmp (string replace -r '^'"$realhome"'($|/)' '~$1' $PWD)
274     285     ---> source /usr/local/Cellar/fish/3.3.1/share/fish/functions/prompt_pwd.fish
151     768     --> prompt_pwd
48      867     ---> if test -z $is_repo...
272     1151    -> printf '%s%s%s' (set_color $fish_color_cwd) (prompt_pwd) (set_color normal)
40040   40040   ----> command git status -s -b 2> /dev/null
111     40151   ---> set -l git_status_origin (command git status -s -b 2> /dev/null)
27      41174   --> git_prompt
200     41435   -> printf '%s%s ☕️ ' (git_prompt) (kubectl_context)
23      42659   > fish_prompt

Fixed git prompt for repo without origin