When interleaving reads and writes from an unflushed pack, we forgot to
reset the file pointer back to the end of the file before writing more
new objects. This had at least two unfortunate effects:
* The pack data was potentially corrupt, since we could overwrite
previous portions of the file willy-nilly.
* The CountingOutputStream would report more bytes read than the size
of the file, which stored the wrong PackedObjectInfo, which would
cause EOFs during reading.
We already had a test in PackInserterTest which was supposed to catch
bugs like this, by interleaving reads and writes. Unfortunately, it
didn't catch the bug, since as an implementation detail we always read a
full buffer's worth of data from the file when inflating during
readback. If the size of the file was less than the offset of the object
we were reading back plus one buffer (8192 bytes), we would completely
accidentally end up back in the right place in the file.
So, add another test for this case where we read back a small object
positioned before a large object. Before the fix, this test exhibited
exactly the "Unexpected EOF" error reported at crbug.com/gerrit/7668.
Change-Id: I74f08f3d5d9046781d59e5bd7c84916ff8225c3b
Dave Borowitz
43ef5dabf1