[regression?] trailing slash required in .gitattributes

[Jeff King <peff@peff.net>]

Prior to v1.8.1.1, if I did this:

  git init
  echo content >foo &&
  mkdir subdir &&
  echo content >subdir/bar &&
  echo "subdir export-ignore" >.gitattributes
  git add . &&
  git commit -m one &&
  git archive HEAD | tar tf -

my archive would contain only "foo" and ".gitattributes", not subdir. As
of v1.8.1.1, the attribute on subdir is ignored unless it is written
with a trailing slash, like:

  subdir/ export-ignore

The issue bisects to 94bc671 (Add directory pattern matching to
attributes, 2012-12-08). That commit actually tests not only that
"subdir/" matches, but also that just "subdir" does not match.

The commit message there is vague about the reasoning, but my
understanding is that it was meant to harmonize gitignore and
gitattributes, the former of which can take "dir/". I don't have a
problem with offering "dir/" to match only directories, but what is the
point in disallowing just "dir" to match a directory?

It seems like a pointless regression to me, but I'm not clear whether it
was intentional or not (and if it was intentional, I think we would need
to handle it with a proper transition period, not in a maint release).

-Peff