Merge pull request #4789 from pks-t/pks/licensing

docs: clarify and include licenses of dependencies

deps/zlib/COPYING

+Copyright (C) 1995-2017 Jean-loup Gailly and Mark Adler
+
+This software is provided 'as-is', without any express or implied
+warranty. In no event will the authors be held liable for any
+damages arising from the use of this software.
+
+Permission is granted to anyone to use this software for any
+purpose, including commercial applications, and to alter it and
+redistribute it freely, subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you
+   must not claim that you wrote the original software. If you
+   use this software in a product, an acknowledgment in the
+   product documentation would be appreciated but is not
+   required.
+
+2. Altered source versions must be plainly marked as such, and
+   must not be misrepresented as being the original software.
+
+3. This notice may not be removed or altered from any source
+   distribution.
+
+Jean-loup Gailly       Mark Adler
+
+The data format used by the zlib library is described by RFCs
+(Request for Comments) 1950 to 1952 in the files rfc1950 (zlib
+format), rfc1951 (deflate format) and rfc1952 (gzip format).

docs/contributing.md

@@ -6,13 +6,22 @@ your help.
 ## Licensing
 
 By contributing to libgit2, you agree to release your contribution under
-the terms of the license.  Except for the `examples` directory, all code
-is released under the [GPL v2 with linking exception](COPYING).
+the terms of the license.  Except for the `examples` and the
+`deps` directories, all code is released under the [GPL v2 with
+linking exception](../COPYING).
 
 The `examples` code is governed by the
-[CC0 Public Domain Dedication](examples/COPYING), so that you may copy
+[CC0 Public Domain Dedication](../examples/COPYING), so that you may copy
 from them into your own application.
 
+The bundled dependencies in the `deps` directories are governed
+by the following licenses:
+
+- http-parser is licensed under [MIT license](../deps/http-parser/COPYING)
+- regex is governed by [LGPL v2.1+ license](../deps/regex/COPYING)
+- winhttp is governed by [LGPL v2.1+](../deps/winhttp/COPYING.LGPL) and [GPL v2 with linking exception](../deps/winhttp/COPYING.GPL)
+- zlib is governed by [zlib license](../deps/zlib/COPYING)
+
 ## Discussion & Chat
 
 We hang out in the