Re: [PATCH] t2400: Fix test failures when using grep 2.5

Phillip Wood [off-list ref] writes:

One thing I forgot to mention was that I think it would be better to
explain in the commit message that "\s" etc. are not part of POSIX
EREs and that is why they do not work.

Yes, that is a very good point.  We have been burned by regular
expression implementations that use or do not use "enhanced" bit in
the recent past, IIRC.

I think it might be better to just diagnose if HEAD is a dangling
symbolic-ref or contains an invalid oid and leave it at that. See the
documentation in refs.h for refs_resolve_ref_unsafe() for how to check
if HEAD is a dangling symbolic ref - if rego_get_oid(repo, "HEAD")
fails and it is not a dangling symbolic ref then it contains an
invalid oid.

Sounds doable and sensible.  If we can easily test it without
peeking into the filesystem, that would be very good.

Thanks.