PS1 : Show git branch only when non-master.

.config/bash/module/ps1.sh

@@ -45,7 +45,9 @@ __prompt_command()
 
   # Add git branch if available.
   local git_branch="$(_git_current_branch)"
-  [[ "${git_branch}" = "" ]] || PS1+=" ${color_blue}@${git_branch}"
+  if [[ "${git_branch}" != "" ]]; then
+    [[ "${git_branch}" =~ (master|main) ]] || PS1+=" ${color_bblue}@${git_branch}"
+  fi
 
   # set error red
   if $is_error; then