This partially reverts bdec62dce1 which activates
the transport code-paths which allow you to use a custom TLS implementation
without having to have one at build-time.
However the capabilities describe how libgit2 was built, not what it could
potentially support, bring back the ifdefs so we only say we support HTTPS if
libgit2 was itself built with a TLS implementation.
Avoid declaring old-style functions without any parameters.
Functions not accepting any parameters should be declared with
`void fn(void)`. See ISO C89 $3.5.4.3.
This ensures that when using OpenSSL a safe default set of ciphers
is selected. This is done so that the client communicates securely
and we don't accidentally enable unsafe ciphers like RC4, or even
worse some old export ciphers.
Implements the first part of https://github.com/libgit2/libgit2/issues/3682
Allow users to set the `git_libgit2_opts` search path for the
`GIT_CONFIG_LEVEL_PROGRAMDATA`. Convert `GIT_CONFIG_LEVEL_PROGRAMDATA`
to `GIT_SYSDIR_PROGRAMDATA` for setting the configuration.
