Jeff King authored Mar 28, 2017 and Junio C Hamano committed Mar 30, 2017

When name-rev needs to format an actual name, we do so into
a fixed-size buffer. That includes the actual ref tip, as
well as any traversal information. Since refs can exceed
1024 bytes, this means you can get a bogus result. E.g.,
doing:

   git tag $(perl -e 'print join("/", 1..1024)')
   git describe --contains HEAD^

results in ".../282/283", when it should be
".../1023/1024~1".

We can solve this by using a heap buffer. We'll use a
strbuf, which lets us write into the same buffer from our
loop without having to reallocate.

Signed-off-by: Jeff King <peff@peff.net>