Allow building libgit2 with Chromium zlib (libgit2#831)

This change allows the caller to set the `USE_CHROMIUM_ZLIB=ON`
environment variable to use the Chromium implementation of zlib when
building libgit2.

Add support for Repository.ReachableFromAny() (libgit2#826)

This change exposes the binding for `git_graph_reachable_from_any()`.

Add support for Odb.MultiPackIndex() (libgit2#819)

This change exposes the binding for `git_odb_write_multi_pack_index()`.

Expose the ssh.PublicKey into the CertificateCheckCallback (libgit2#818)

This change exposes the raw SSH hostkey and the ssh.PublicKey into the
CertificateCheckCallback, so that callers can do better validations.

libgit2 v1.2.0 #major

This commit introduces libgit2 v1.2.0 to git2go, which brings a large
number of [bugfixes and
features](https://github.com/libgit2/libgit2/releases/tag/v1.2.0).

This also marks the start of the v32 release.

Allow building libgit2 with Chromium zlib (libgit2#831) (libgit2#833)

This change allows the caller to set the `USE_CHROMIUM_ZLIB=ON`
environment variable to use the Chromium implementation of zlib when
building libgit2.

(cherry picked from commit c6da3b9)

Co-authored-by: lhchavez <[email protected]>

Add support for managed SSH transport #minor (libgit2#814)

This change drops the (hard) dependency on libssh2 and instead uses Go's
implementation of SSH when libgit2 is not built with it.

Allow building libgit2 with Chromium zlib (libgit2#831) (libgit2#832)

This change allows the caller to set the `USE_CHROMIUM_ZLIB=ON`
environment variable to use the Chromium implementation of zlib when
building libgit2.

(cherry picked from commit c6da3b9)

Co-authored-by: lhchavez <[email protected]>

Add support for managed SSH transport #minor (libgit2#814) (libgit2#815)

This change drops the (hard) dependency on libssh2 and instead uses Go's
implementation of SSH when libgit2 is not built with it.

(cherry picked from commit 70e5e41)

Co-authored-by: lhchavez <[email protected]>

Add support for managed SSH transport #minor (libgit2#814) (libgit2#816)

This change drops the (hard) dependency on libssh2 and instead uses Go's
implementation of SSH when libgit2 is not built with it.