There is a long standing issue with C Git pushing to Gerrit and Jgit
where the occasional push will fail because the negotiated packs are
missing a tree object. This happens very occasionally but when it does
it would be nice to be able to point users at an easy workaround.
Pushing with --no-thin is that workaround.
Note that --no-thin is much less efficient so shouldn't be used by
default.
This old bug, https://bugs.launchpad.net/git-review/+bug/1332549, has
details but it seems to affect current C git and Gerrit+Jgit.
Change-Id: Id6ba52a656a14c921acab1b14ef668e6251245da
39cd763d5d