Change to use omz git_prompt* functions

Removed references for official git __git_ps1() functions.
Change to use omz function git_prompt* functions like:
- git_prompt_info() -> branch name
- git_prompt_status() -> check if untracked, modified, added,
  stashed file are in the current git repo
- git_remote_status() -> check if current repo is ahead, behind,
  or diverged.
These functions returns string automatically added to your PS1;
these are customizable via exporting ZSH_THEME_GIT_PROMPT*

themes/michelebologna.zsh-theme

@@ -59,16 +59,17 @@ ZSH_THEME_GIT_PROMPT_PREFIX=""
 ZSH_THEME_GIT_PROMPT_SUFFIX=""
 ZSH_THEME_GIT_PROMPT_DIRTY=""
 ZSH_THEME_GIT_PROMPT_CLEAN=""
-ZSH_THEME_GIT_PROMPT_UNTRACKED="%%"
-ZSH_THEME_GIT_PROMPT_MODIFIED="*"
-ZSH_THEME_GIT_PROMPT_ADDED="+"
-ZSH_THEME_GIT_PROMPT_STASHED="$"
-ZSH_THEME_GIT_PROMPT_EQUAL_REMOTE="="
+ZSH_THEME_GIT_PROMPT_UNTRACKED="$blue%%"
+ZSH_THEME_GIT_PROMPT_MODIFIED="$red*"
+ZSH_THEME_GIT_PROMPT_ADDED="$green+"
+ZSH_THEME_GIT_PROMPT_STASHED="$blue$"
+ZSH_THEME_GIT_PROMPT_EQUAL_REMOTE="$green="
 ZSH_THEME_GIT_PROMPT_AHEAD_REMOTE=">"
 ZSH_THEME_GIT_PROMPT_BEHIND_REMOTE="<"
-ZSH_THEME_GIT_PROMPT_DIVERGED_REMOTE="<>"
+ZSH_THEME_GIT_PROMPT_DIVERGED_REMOTE="$red<>"
 
 PROMPT='$username_output$hostname_output:$current_dir_output%1(j. [$jobs_bg].)'
-PROMPT+='$(__git_ps1)'
+GIT_PROMPT='$(out=$(git_prompt_info)$(git_prompt_status)$(git_remote_status);if [[ -n $out ]]; then printf %s " $white($green$out$white)$reset";fi)'
+PROMPT+="$GIT_PROMPT"
 PROMPT+=" $last_command_output%#$reset "
 RPROMPT=''