refactor: enhance current_branch function for better detection

Update the current_branch function to handle cases where the branch is either empty or set to HEAD, normalizing the output to indicate a detached state. Additionally, refactor cmd_list to utilize the updated current_branch function, improving code clarity and maintainability.

Author: helizaga

bin/gtr

@@ -1055,10 +1055,7 @@ cmd_list() {
   if [ "$porcelain" -eq 1 ]; then
     # Output: path<tab>branch<tab>status
     local branch status
-    branch=$(get_current_branch "$repo_root")
-    if [ -z "$branch" ] || [ "$branch" = "HEAD" ]; then
-      branch="(detached)"
-    fi
+    branch=$(current_branch "$repo_root")
     status=$(worktree_status "$repo_root")
     printf "%s\t%s\t%s\n" "$repo_root" "$branch" "$status"
 
@@ -1086,10 +1083,7 @@ cmd_list() {
 
   # Always show repo root first
   local branch
-  branch=$(get_current_branch "$repo_root")
-  if [ -z "$branch" ] || [ "$branch" = "HEAD" ]; then
-    branch="(detached)"
-  fi
+  branch=$(current_branch "$repo_root")
   printf "%-30s %s\n" "$branch [main repo]" "$repo_root"
 
   # Show worktrees sorted by branch name

lib/core.sh

@@ -166,8 +166,8 @@ current_branch() {
   local branch
   branch=$(get_current_branch "$worktree_path")
 
-  # Normalize detached HEAD
-  if [ "$branch" = "HEAD" ]; then
+  # Normalize detached HEAD or empty (failed detection)
+  if [ -z "$branch" ] || [ "$branch" = "HEAD" ]; then
     branch="(detached)"
   fi