Jakub Narębski [off-list ref] writes:
Especially that for submodules you need:
$ git --git-dir=subdir/.git cat-file -p $(git rev-parse HEAD:subdir):file
(or something like that), assuming that you start in supermodule.
...
But perhaps '//' would be better.
If the users have to know where they need to use different
separator, I do not think it is worth complicating the plumbing to
do this for them. I'd rather keep things simple, and let the users
build complex stuff on top of the plumbing.