Improve logic for checking if inside a git repo

prompt.zsh

@@ -34,8 +34,10 @@ zstyle ':vcs_info:git*' actionformats ' %b|%a'
 
 # Fastest possible way to check if repo is dirty
 git_dirty() {
-	[ -d .git ] || return
-	command git diff --quiet --ignore-submodules HEAD 2>/dev/null; [ $? -eq 1 ] && echo '*'
+	# check if we're in a git repo
+	command git rev-parse --is-inside-work-tree &>/dev/null || return
+	# check if it's dirty
+	command git diff --quiet --ignore-submodules HEAD &>/dev/null; [ $? -eq 1 ] && echo '*'
 }
 
 # Displays the exec time of the last command if set threshold was exceeded