simple version of bash git prompt for ksh (also works in bash) (raw escape, click raw and fetch the gist URL with curl or wget)

prompt.sh

shopt -s checkwinsize 2>/dev/null

_cmd_status() {
    if [ $? -eq 0 ]; then
        printf '\001\002✔'
    else
        printf '\001\002✘'
    fi
}

_git_branch() {
    _br="$(git rev-parse --abbrev-ref HEAD 2>/dev/null)"

    if [ -n "$_br" ]; then
        printf '\001\002[\001\002'"${_br}"'\001\002]\001\002'
    fi
}

PS1='`_cmd_status`  \001\002\w `_git_branch`\n\001\002'"${USER}"'\001\002@\001\002\h  \001\002➤\001\002  '

With older version of this script I sometimes got -bash: [: 1: unary operator expected after various git commands:

++ history -a
++ set_prompt
++ git --no-pager branch --no-color
+++ _git_branch
+++ local i c=1 only_local_ref=n has_r=n
+++ '[' 1 -lt ']'
-bash: [: 1: unary operator expected

Perhaps there's namespace clash with bash completion project:

/usr/share/bash-completion/completions/git:_git_branch ()
/usr/share/bash-completion/completions/gitk:_git_branch ()