Bug in reflog of length 0x2BFF

Hi,

I encountered a strange bug concerning the reflog.
I suspect some kind of out-of-bounds access.
The symptom is:

%git rev-parse 'master@{52}'
warning: Log for ref refs/heads/master has gap after Thu, 1 Jan 1970
00:00:01 +0000.
0000000000000000000000000000000000000036

Try the following:

git init gitbug
cd gitbug
git commit --allow-empty -m a
cp ../reflog.bad .git/logs/refs/heads/master
git rev-parse 'master@{52}'

The source of cp is the attached file.
This is from a reflog of stash.
I just replaced all stuff by dummy values.
This does not seem to affect the bug.
Sorry, it must be this long.

Some observations:
* If you change the length of any line starting at line 3, the symptom
vanishes.
  (The XXXXX at the line ends are free-form text.)
* Starting at line three, there are 0x2BFF bytes till the end of file.
  Is there some dynamically growing buffer, which at some point reaches
the size 0x2C00?
* Changing the length of the first two lines has no effect.
  Is the file read backwards?
* It happens at least with git 2.1.2 (amd64) and 2.2.0 (ia32).
* 2.0.2 (amd64) and 2.1.0 (amd64) seem not to have this bug.


Any ideas?

	Christoph