Fix regressions in the prompt

prompt

@@ -54,7 +54,7 @@ prompt_chars() {
     if $(git rev-parse --is-inside-work-tree >/dev/null 2>&1); then
         local git_char="%{$fg_no_bold[blue]%}±%{$reset_color%}"
     fi
-    printf "${_GIT_CHAR}$(last_status) $(color_prompt_char)"
+    printf "%s" "${_GIT_CHAR}$(last_status) $(color_prompt_char)"
 }
 
 charge_batterie() {
@@ -133,11 +133,10 @@ vim_mode () {
 # %r - The name of the root directory of the repository
 # %s - The current version control system, like git or svn
 # %u - unstagedstr (see below)
-vcs_color='blue'
 fmt_branch="%b%{$reset_color%} %u%c%m%{$reset_color%}" # e.g. master¹²
 fmt_action="(%{$fg[red]%}%a%{$reset_color%})"   # e.g. (rebase-i)
-fmt_pre="%{$fg_bold[$vcs_color]%}[%{$reset_color%}%{$fg[$vcs_color]%}"
-fmt_post="%{$fg_bold[$vcs_color]%}]%{$reset_color%}"
+fmt_pre="%{$fg_bold[blue]%}[%{$reset_color%}%{$fg[blue]%}"
+fmt_post="%{$fg_bold[blue]%}]%{$reset_color%}"
 
 # check-for-changes can be really slow.
 # you should disable it, if you work with large repositories