feat(git): support trunk branches in `git_main_branch` (#9417)

plugins/git/git.plugin.zsh

@@ -31,11 +31,14 @@ function work_in_progress() {
 
 # Check if main exists and use instead of master
 function git_main_branch() {
-  if [[ -n "$(git branch --list main)" ]]; then
-    echo main
-  else
-    echo master
+  local branch
+  for branch in main trunk; do
+    if command git show-ref -q --verify refs/heads/$branch; then
+      echo $branch
+      return
     fi
+  done
+  echo master
 }
 
 #