fetchhead reading/iterating

netops: on SSL teardown only send shutdown alert

Make `goto cleanup` more consistent

RFC: Some cleanups/features in CMakeLists.txt

Fix some leaks in tests

Also adds some asserts.

... so we can clean up correctly.

Instead tell MSVC to group the source files by directory.

- Also document the -DSTDCALL even better.

With the src/compat/*.c glob removed, there is no longer a difference to
the default globs we use for the IF( UNIX ) case.

This directory doesn't exist.

Up to now, on windows we don't even bother to look if the user has a zlib
available somwhere.

In almost all larger commercial projects i've participated in, it was not
at all uncommon to have such a dependency somewhere in the source tree and
use it whereever required.
Searching for it, even if it's unlikely to be present, allows for such a
scenario (i.e. by prefilling the CMake-Cache).

There may be some question about whether this is likely to be needed
at all, but that's above my head at the moment.

don't deref before we've asserted

just sayin'.

Trivial comment fix

I was totally flaunting @ben's 3-space tab advice.

This looked wrong to me.  I *think* this is more appropriate
commentary.

Reset global variable to NULL after free'ing resource

Fix diff constructor names

Based on feedback from the ObjectiveGit folks, these are some
further updates to diff.h areas that are poorly documented.

The diff constructor functions had some confusing names, where the
"old" side of the diff was coming after the "new" side.  This
reverses the order in the function name to make it less confusing.

Specifically...

* git_diff_index_to_tree becomes git_diff_tree_to_index
* git_diff_workdir_to_index becomes git_diff_index_to_workdir
* git_diff_workdir_to_tree becomes git_diff_tree_to_workdir

According to man 3 SSL_shutdown / TLS, "If a unidirectional shutdown is
enough (the underlying connection shall be closed anyway), this first
call to SSL_shutdown() is sufficient."

Currently, an unidirectional shutdown is enough, since
gitno_ssl_teardown is called by gitno_close only. Do so to avoid further
errors (by misbehaving peers for example).

Fixes #1129.

Don't return an error just because GITNO_CONNECT_SSL_NO_CHECK_CERT is
set.

Introduce git_blob_is_binary()

Cleanup the empty-clone test correctly