v0.21 + 1
------

* File unlocks are atomic again via rename. Read-only files on Windows are
  made read-write if necessary.

* Share open packfiles across repositories to share descriptors and mmaps.

* Use a map for the treebuilder, making insertion O(1)

* Introduce reference transactions, which allow multiple references to
  be locked at the same time and updates be queued. This also allows
  us to safely update a reflog with arbitrary contents, as we need to
  do for stash.

* LF -> CRLF filter refuses to handle mixed-EOL files

* LF -> CRLF filter now runs when * text = auto (with Git for Windows 1.9.4)

* The git_transport structure definition has moved into the sys/transport.h
  file.

* The ssh transport supports asking the remote host for accepted
  credential types as well as multiple challeges using a single
  connection. This requires to know which username you want to connect
  as, so this introduces the USERNAME credential type which the ssh
  transport will use to ask for the username.

* The git_transport_register function no longer takes a priority and takes
  a URL scheme name (eg "http") instead of a prefix like "http://"

* The git_remote_set_transport function now sets a transport factory function,
  rather than a pre-existing transport instance.

* A factory function for ssh has been added which allows to change the
  path of the programs to execute for receive-pack and upload-pack on
  the server, git_transport_ssh_with_paths.

* The git_clone_options struct no longer provides the ignore_cert_errors or
  remote_name members for remote customization.

  Instead, the git_clone_options struct has two new members, remote_cb and
  remote_cb_payload, which allow the caller to completely override the remote
  creation process. If needed, the caller can use this callback to give their
  remote a name other than the default (origin) or disable cert checking.

  The remote_callbacks member has been preserved for convenience, although it
  is not used when a remote creation callback is supplied.

* The git_clone_options struct now provides repository_cb and
  repository_cb_payload to allow the user to create a repository with
  custom options.

* The option to ignore certificate errors via git_remote_cert_check()
  is no longer present. Instead, git_remote_callbacks has gained a new
  entry which lets the user perform their own certificate checks.

* git_clone_into and git_clone_local_into have been removed from the
  public API in favour of git_clone callbacks

* Add support for refspecs with the asterisk in the middle of a
  pattern.

* Fetching now performs opportunistic updates. To achieve this, we
  introduce a difference between active and passive refspecs, which
  make git_remote_download and git_remote_fetch to take a list of
  resfpecs to be the active list, similarly to how git fetch accepts a
  list on the command-line.

* Introduce git_merge_bases() and the git_oidarray type to expose all
  merge bases between two commits.

* Introduce git_merge_bases_many() to expose all merge bases between
  multiple commits.
