feat(git): add comprehensive git folder management commands and update documentation

bin/sync-git-folder

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+sync-git-folder() {
+    if [[ -z "$1" ]]; then
+        echo '$1/branch is empty.'
+        exit
+    fi
+    if [[ -z "$2" ]]; then
+        echo '$2/path is empty.'
+        exit
+    fi
+
+    echo 'Switch and pull git folders.'
+    switch-git-folder "$"
+    pull-git-folder "$1" "$1"
+}