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
git_index_read_tree() was exposing a parameter to provide the user with
a progress indicator. Unfortunately, due to the recursive nature of the
tree walk, the maximum number of items to process was unknown. Thus,
the indicator was only counting processed entries, without providing
any information how the number of remaining items.
This fixes git_index_add and git_index_append to behave more like
core git, preserving old filemode data in the index when adding
and/or appending with core.filemode = false.
This also has placeholder support for core.symlinks and
core.ignorecase, but those flags are not implemented (well,
symlinks has partial support for preserving mode information in
the same way that git does, but it isn't tested).
