raise util.CommandError('Only a single head is supported. The '
alembic.util.CommandError: Only a single head is supported. The script directory has multiple heads (due to branching), which must be resolved by manually editing the revision files to form a linear sequence. Run alembic branches to see the pergence(s).

• flask博客部署到heroku时，在pus到heroku后运行时报错。貌似是git 分支的问题？不知道怎么解决。

• 我找到了一段解决方法： this happens when you go back to a revision that is not the last and then create a new migration. Now you have two branches, which Alembic cannot handle. Look at how the migration files are chained together through migration ids, you need to create a linear chain to collapse the branches.

• 看的不太懂。不知道how?

• 十分感谢。