增加清理附件按钮，对悬空无引用的图片/附件进行清理 (#918)

* add attach_clean & change_theme

* add attach_clean & change_theme

* add

* add readme

---------

Co-authored-by: root <root@DESKTOP-L84EQPB.localdomain>

database/clean.py

@@ -0,0 +1,34 @@
+import sqlite3
+import os, glob
+
+conn = sqlite3.connect("mindoc.db")
+cur = conn.cursor()         #通过建立数据库游标对象，准备读写操作
+
+
+cmd = """
+SELECT 
+    att.http_path
+FROM
+    md_attachment AS att
+WHERE (att.document_id != 0 OR (NOT EXISTS( SELECT 1 FROM md_documents WHERE markdown LIKE ("%" || att.http_path || "%"))))
+AND (att.document_id = 0 OR (NOT EXISTS( SELECT 1 FROM md_documents WHERE att.document_id = document_id )))
+"""
+cur.execute(cmd)
+file_list = cur.fetchall()
+for file_item in file_list:
+    item_path = file_item[0]
+    # 1. 删除os文件
+    if os.path.exists(os.path.join("..", item_path[1:])):
+        os.remove(os.path.join("..", item_path[1:]))
+    
+    # 2. 查询os是否删除成功，成功则删除附件记录
+    if not os.path.exists(os.path.join("..", item_path[1:])):
+        cmd = """
+        delete
+        from md_attachment
+        WHERE http_path = '{}'
+        """.format(item_path)
+        cur.execute(cmd)
+conn.commit()   #保存提交，确保数据保存成功
+
+conn.close()        #关闭与数据库的连接