> Commands that support the enhanced option parser accepts unique prefix of a long option as if it is fully spelled out, but use this with a caution. For example, git commit --amen behaves as if you typed git commit --amend, but that is true only until a later version of Git introduces another option that shares the same prefix, e.g. git commit --amenity option.

Of course that makes many flag additions technically breaking changes. This could be a surprise because if you accidentally dropped some characters you would have no warning until a Git update breaks it.

The git man page explicitly says that if you're writing a script of git commands, you should use the full option name, so you won't encounter this ambiguous issue.

So no, it doesn't constraint the evolution of the API.