CRAN release v0.12.1

git2r 0.12.1

NEW FEATURES

• Add 'remote_ls' method to list references in a remote repository akin to the
  git ls-remote command.
• Add 'remote_set_url' method to set the remote's url in the
  configuration.
• Add 'cred_token' S4 class to hold the name of the environmental
  variable with the secret. Default value for the name is GITHUB_PAT.
• It is now possible to checkout a specific file with the 'checkout'
  method.
• Add 'ssl_cert_locations' method to set libgit2 global option
  'GIT_OPT_SET_SSL_CERT_LOCATIONS'
• Add 'ceiling' argument to 'discover_repository' method to prevent
  search from walking up the parent directories.

CHANGES

• Improvments to the cred_* functions documentation.
• Add the following default arguments to the 'cred_ssh_key' method:
  publickey = '/.ssh/id_rsa.pub' and privatekey = '/.ssh/id_rsa'
• On OSX, cascade CPPFLAGS and LDFLAGS to libssh2 build to allow
  libssh2 to be built against a user-installed openssl, discovered by
  configure or from R's Makeconf. Necessary to build on OS X ≥ 10.11
• On OS X, SecureTransport is now used to provide the cryptographic
  support for HTTPS connections insead of OpenSSL.
• The search for libssh2 during configuration (non Windows) is now
  done via pkg-config.
• Update OpenSSL on Windows to v1.0.2d
• Update libgit2 source code to commit (3f5877d) from 2015-11-12.

BUG FIXES

• Add missing credentials argument to pull method.
• Fix config failure when user.name or user.email are passed as
  variables.
• Include 'configure.ac' in the distribution.