The previous message is included in the error:

 ! [remote rejected] master -> refs/patches (patch commits are already included in the base branch)

To make it clearer to the user, also print a warning to tell them that the commit was in the base branch – including the commit SHA:

warn: attempted to create a patch using the commit f2de534b5e81d7c6e2dcaf58c3dd91573c0a0354, but this commit is already included in the base branch

Rebase