'next'ed --allow-unrelated-histories could cause lots of grief

Dear Git Gurus,

I guess whenever it rains it indeed pours, so it is me whining again.

I have decided to try 2.8.1.369.geae769a available from debian experimental and through our (datalad) tests failing I became aware of the

    https://github.com/git/git/pull/158/commits/e379fdf34fee96cd205be83ff4e71699bdc32b18
    merge: refuse to create too cool a merge by default

which is planned for the next release. I guess it is indeed a worthwhile accident-prevention measure BUT not sure if it is so important as to cause a change in behavior on which some projects using git through the cmdline interface might have been relying upon for years!

Given that git is quite 'self-healing', i.e. if someone has managed to make a merge he didn't intend to, there is always a way back (e.g., as simple as git reset --hard HEAD^), I am really not sure how valuable such change of default behavior would be? Could it may be made into a warning instead? or reversed option "--dont-allow-unrelated-histories"?

Moreover, it was explicitly stated that "no configuration variable to enable this by default exists and will not be added", which would cause 3rd party scripts/code/projects relying on previous behavior to provide version specific handling (either to add that --allow-unrelated-histories or not)... very cumbersome! If nothing else remains, could there at least be a config option which we could then use regardless of the version of git we are using for such merges?

P.S. Please maintain CC list

Thank you in advance for your consideration,