It's hard to remember whether it's `-DUSE_HTTPS=mbedTLS` or
`-DUSE_HTTPS=mbedtls`. Even worse for things like `builtin` which we may
have been inconsistent about. Allow for case insensitive options.
There were a few oddities around HTTPS provider selection: namely,
`GIT_OPENSSL_DYNAMIC` implied `GIT_OPENSSL`, which made a bit of sense,
until we added FIPS support. In addition, dynamic OpenSSL for _hashes_
and dynamic OpenSSL for HTTPS was conflated in a few places.
Untangle these, and make `GIT_HTTPS_*` the define, for consistency with
other feature provider selection.
since f15c8ac71a libgit unconditionally depends on secur32 on Windows
but only added it in cmake for the winhttp and schannel variants.
In case libgit is built against openssl it would fail to link.
This moves secur32 out of the https backend selection code into
the global win32 condition (and while at it also adds ws2_32 to the .pc file)
Provide a stream interface for Schannel - the native crypto APIs - on
Windows. This allows Windows to use the same HTTP transport that all the
other platforms use, with its own native crypto.
Ultimately this allows us to deprecate WinHTTP and we need not add
support for our socket changes in two places (our HTTP stack and the
WinHTTP stack).
Provide an interface around OpenSSL to dynamically load the libraries
and symbols, so that users can distribute a libgit2 library that is not
linked directly against OpenSSL. This enables users to target multiple
distributions with a single binary.
This mechanism is optional and disabled by default. Configure cmake
with -DUSE_HTTPS=OpenSSL-Dynamic to use it.
Our custom CMake module currently live in "cmake/Modules". As the
"cmake/" directory doesn't contain anything except the "Modules"
directory, it doesn't really make sense to have the additional
intermediate directory. So let's instead move the modules one level up
into the "cmake/" top level directory.
