Kevin Ballard [off-list ref] writes:
Another possibility is using this new behavior for core.excludesfile and
possibly .git/info/exclude, but not for patterns in .gitignore
files.
I suspect that that approach is totally unacceptable. These out-of-tree
exclude pattern files do not have any semantic difference from the in-tree
exclude pattern files (.gitignore); it makes no sense to make them
syntactically different.
More importantly it is much harder to diagnose if you break people's
private configuration without introducing the same breakage to what's
available to wider public guinea pigs.