feat(zsh): drop ohmyzsh+git for custom aliases

zsh/scripts.zsh

@@ -1,3 +1,20 @@
+# git helpers for aliases
+function git_current_branch {
+    command git rev-parse --abbrev-ref HEAD 2>/dev/null
+}
+
+function git_main_branch {
+    command git rev-parse --git-dir &>/dev/null || return
+    local ref
+    for ref in refs/{heads,remotes/{origin,upstream}}/{main,master,trunk}; do
+        if command git show-ref -q --verify "$ref"; then
+            echo ${ref:t}
+            return 0
+        fi
+    done
+    echo main
+}
+
 function tmux_attach {
     local tmux_running
     tmux_running=$(pgrep tmux)