Without this change, any failed assertion in the second (or a later) test
inside a test suite has a chance of double deleting memory, resulting in
a heap corruption. See #1096 for details.
This leaves alone the test cases where we "just" use cl_git_sandbox_init()
and cl_git_sandbox_cleanup(). These methods already take good care to not
double delete a repository.
Fixes#1096
We used to require loose references to contain only an OID (possibly
after trimming the string). This is however not enough for letting us
lookup FETCH_HEAD, which can have a lot of content after the initial
OID.
Change the parsing rules so that a loose refernce must e at least 40
bytes long and the 41st (if it's there) must be accepted by
isspace(3). This makes the trim unnecessary, so only do it for
symrefs. This fixes#977.
