什么是"svn:警告:W155010:节点不是外部的"是什么意思？

我试图用来svn:externals自动检出另一个目录下的某个目录的副本.这是我的项目在存储库中的目录的示例:

trunk
  releases
    releases_1_4
      database
      conf
      resources
      etl_machines
      workflows

然后我想创建一个名为release_1_4_1的副本release_1_4,因此我添加了一个externals属性,releases如下所示:

$ svn propset svn:externals 'http://server/svn/repos/MAIN/releases/branches/2012-09-13_branch/releases/release_1_4@38320 release_1_4_1'

现在,如果我签入该属性更改,然后进行更新,我会收到如下错误:

$ svn update
Updating '.':

Fetching external item into 'release_1_4_1':
A    release_1_4_1/a_file
A    release_1_4_1/database
A    release_1_4_1/database/a.sql
A    release_1_4_1/database/b.sql
A    release_1_4_1/database/c.sql
A    release_1_4_1/conf
A    release_1_4_1/conf/prod.properties
A    release_1_4_1/conf/dev.properties
A    release_1_4_1/conf/test.properties
A    release_1_4_1/resources
A    release_1_4_1/resources/a
A    release_1_4_1/resources/a/install.groovy
A    release_1_4_1/etl_machines
A    release_1_4_1/etl_machines/b
A    release_1_4_1/etl_machines/b/start_services.groovy
A    release_1_4_1/etl_machines/b/install.groovy
A    release_1_4_1/workflows
A    release_1_4_1/workflows/cm
A    release_1_4_1/workflows/cm/install.groovy
Updated external to revision 38320.

svn: warning: W200000: Error handling externals definition for 'release_1_4_1/etl_machines':
svn: warning: W155010: The node '/home/user/wcs/trunk/releases/release_1_4_1/etl_machines' is not an external.
svn: warning: W200000: Error handling externals definition for 'release_1_4_1/workflows':
svn: warning: W155010: The node '/home/user/wcs/trunk/releases/release_1_4_1/workflows' is not an external.
svn: warning: W200000: Error handling externals definition for 'release_1_4_1/cm':
svn: warning: W155010: The node '/home/user/wcs/trunk/releases/release_1_4_1/cm' is not an external.
svn: warning: W200000: Error handling externals definition for 'release_1_4_1/database':
svn: warning: W155010: The node '/home/user/wcs/trunk/releases/release_1_4_1/database' is not an external.
svn: warning: W200000: Error handling externals definition for 'release_1_4_1/conf':
svn: warning: W155010: The node '/home/user/wcs/trunk/releases/release_1_4_1/conf' is not an external.
svn: warning: W200000: Error handling externals definition for 'release_1_4_1/resources':
svn: warning: W155010: The node '/home/user/wcs/trunk/releases/release_1_4_1/resources' is not an external.
At revision 43894.
svn: E205011: Failure occurred processing one or more externals definitions

知道我在这里做错了吗？(svn版本1.8.1)