我是git的新手，我创建了多个分支以将较大的更改文件拆分为20个提交，并希望进行堆叠式PR。但是我无法基于先前的分支拉请求（已经将请求拉到github中）。如果您能给我一些建议以解决它，我将不胜感激。
这是代码，我已经从“ issue12205_2”分支中放入了PR， 但是，当我切换到分支'issue12205_3'并想基于分支issue12205_2创建PR时，出现错误：“ base”的值无效
(venv) cch:incubator-mxnet cch$ git show-branch
! [issue12205] solve pylint errors in examples with issue no.12205
! [issue12205_2] [issue_12205 - PART1]
* [issue12205_3] [issue_12205 - PART2]
! [issue12205_4] [issue_12205 - PART3]
! [issue12205_5] [issue_12205 - PART4]
! [issue12205_6] [issue_12205 - PART5]
! [issue12205_7] [issue_12205 - PART6]
! [issue12205_8] [issue_12205 - PART7]
! [issue12205_9] [issue_12205 - PART8]
! [issue12205_10] [issue_12205 - PART9]
! [issue12205_11] [issue_12205 - PART10]
! [issue12205_12] [issue_12205 - PART11]
! [issue12205_13] [issue_12205 - PART12]
! [issue12205_14] [issue_12205 - PART13]
! [issue12205_15] [issue_12205 - PART14]
! [issue12205_16] [issue_12205 - PART15]
! [issue12205_17] [issue_12205 - PART16]
! [issue12205_18] [issue_12205 - PART17]
! [issue12205_19] [issue_12205 - PART18]
! [issue12205_20] [issue_12205 - PART19]
! [issue12205_21] [issue_12205 - PART20]
! [master] AdamW operator (Fixing Weight Decay Regularization in Adam) (#13728)
----------------------
+ [issue12205_21] [issue_12205 - PART20]
++ [issue12205_20] [issue_12205 - PART19]
+++ [issue12205_19] [issue_12205 - PART18]
++++ [issue12205_18] [issue_12205 - PART17]
+++++ [issue12205_17] [issue_12205 - PART16]
++++++ [issue12205_16] [issue_12205 - PART15]
+++++++ [issue12205_15] [issue_12205 - PART14]
++++++++ [issue12205_14] [issue_12205 - PART13]
+++++++++ [issue12205_13] [issue_12205 - PART12]
++++++++++ [issue12205_12] [issue_12205 - PART11]
+++++++++++ [issue12205_11] [issue_12205 - PART10]
++++++++++++ [issue12205_10] [issue_12205 - PART9]
+++++++++++++ [issue12205_9] [issue_12205 - PART8]
++++++++++++++ [issue12205_8] [issue_12205 - PART7]
+++++++++++++++ [issue12205_7] [issue_12205 - PART6]
++++++++++++++++ [issue12205_6] [issue_12205 - PART5]
+++++++++++++++++ [issue12205_5] [issue_12205 - PART4]
++++++++++++++++++ [issue12205_4] [issue_12205 - PART3]
*++++++++++++++++++ [issue12205_3] [issue_12205 - PART2]
+*++++++++++++++++++ [issue12205_2] [issue_12205 - PART1]
+*+++++++++++++++++++ [master] AdamW operator (Fixing Weight Decay Regularization in Adam) (#13728)
(venv) cch:incubator-mxnet cch$ hub pull-request -b issue12205_2
Error creating pull request: Unprocessable Entity (HTTP 422)
Invalid value for "base"
参考：https://graysonkoonce.com/stacked-pull-requests-keeping-github-diffs-small/