git rebase -i commitId
假设想要合并最后3个commit， git log显示
commit id 1
commit id 2
commit id 3
commit id 4
则执行git rebase -i commitId4. 注意是4，不是3.
然后，pick最老的commit (commit id 3).
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https://blog.csdn.net/qiaoqiaoBigBoss/article/details/113729079
