[RFC] subtree: use say and exit 0 rather than die in case of no new revision found scenario

[Claus Schneider <claus.schneider@xxxxxxxxxxx>]

Hi..

Currently subtree dies if "No new revisions found" which is hard as it
is a non-operation.

I suggest using the "say" command rather than "die".

It will then become easier just to call "git subtree split" and you do
not need to handle this special case.

Patches can be found here:
https://github.com/git/git/commit/fe435a1ba128698f6acb69ee1891c45be32610fa

Best regards
Claus Schneider