This is the first release of the v0.23 series, "Entschuldigung", with many fixes and new features since v0.22.

The largest changes are to the handling of remotes and submodules. We no longer treat them as ORM-like objects, but model the way the Git configuration is updated more closely. These objects now keep their state as of the lookup/refresh time and they're not shared across lookups.

The changelog follows.

Changes or improvements

• Patience and minimal diff drivers can now be used for merges.
• Merges can now ignore whitespace changes.
• Updated binary identification in CRLF filtering to avoid false positives in
  UTF-8 files.
• Rename and copy detection is enabled for small files.
• Checkout can now handle an initial checkout of a repository, making
  GIT_CHECKOUT_SAFE_CREATE unnecessary for users of clone.
• The signature parameter in the ref-modifying functions has been
  removed. Use git_repository_set_ident() and
  git_repository_ident() to override the signature to be used.
• The local transport now auto-scales the number of threads to use
  when creating the packfile instead of sticking to one.
• Reference renaming now uses the right id for the old value.
• The annotated version of branch creation, HEAD detaching and reset
  allow for specifying the expression from the user to be put into the
  reflog.
• git_rebase_commit now returns GIT_EUNMERGED when you attempt to
  commit with unstaged changes.
• On Mac OS X, we now use SecureTransport to provide the cryptographic
  support for HTTPS connections insead of OpenSSL.
• Checkout can now accept an index for the baseline computations via the
  baseline_index member.
• The configuration for fetching is no longer stored inside the
  git_remote struct but has been moved to a git_fetch_options. The
  remote functions now take these options or the callbacks instead of
  setting them beforehand.
• git_submodule instances are no longer cached or shared across
  lookup. Each submodule represents the configuration at the time of
  loading.
• The index now uses diffs for add_all() and update_all() which
  gives it a speed boost and closer semantics to git.
• The ssh transport now reports the stderr output from the server as
  the error message, which allows you to get the "repository not
  found" messages.
• git_index_conflict_add() will remove staged entries that exist for
  conflicted paths.
• The flags for a git_diff_file will now have the GIT_DIFF_FLAG_EXISTS
  bit set when a file exists on that side of the diff. This is useful
  for understanding whether a side of the diff exists in the presence of
  a conflict.
• The constructor for a write-stream into the odb now takes
  git_off_t instead of size_t for the size of the blob, which
  allows putting large files into the odb on 32-bit systems.
• The remote's push and pull URLs now honor the url.$URL.insteadOf
  configuration. This allows modifying URL prefixes to a custom
  value via gitconfig.
• git_diff_foreach, git_diff_blobs, git_diff_blob_to_buffer,
  and git_diff_buffers now accept a new binary callback of type
  git_diff_binary_cb that includes the binary diff information.
• The race condition mitigations described in racy-git.txt have been
  implemented.
• If libcurl is installed, we will use it to connect to HTTP(S)
  servers.

API additions

• The git_merge_options gained a file_flags member.
• Parsing and retrieving a configuration value as a path is exposed
  via git_config_parse_path() and git_config_get_path()
  respectively.
• git_repository_set_ident() and git_repository_ident() serve to
  set and query which identity will be used when writing to the
  reflog.
• git_config_entry_free() frees a config entry.
• git_config_get_string_buf() provides a way to safely retrieve a
  string from a non-snapshot configuration.
• git_annotated_commit_from_revspec() allows to get an annotated
  commit from an extended sha synatx string.
• git_repository_set_head_detached_from_annotated(),
  git_branch_create_from_annotated() and
  git_reset_from_annotated() allow for the caller to provide an
  annotated commit through which they can control what expression is
  put into the reflog as the source/target.
• git_index_add_frombuffer() can now create a blob from memory
  buffer and add it to the index which is attached to a repository.
• The structure git_fetch_options has been added to determine the
  runtime configuration for fetching, such as callbacks, pruning and
  autotag behaviour. It has the runtime initializer
  git_fetch_init_options().
• The enum git_fetch_prune_t has been added, letting you specify the
  pruning behaviour for a fetch.
• A push operation will notify the caller of what updates it indends
  to perform on the remote, which provides similar information to
  git's pre-push hook.
• git_stash_apply() can now apply a stashed state from the stash list,
  placing the data into the working directory and index.
• git_stash_pop() will apply a stashed state (like git_stash_apply())
  but will remove the stashed state after a successful application.
• A new error code GIT_EEOF indicates an early EOF from the
  server. This typically indicates an error with the URL or
  configuration of the server, and tools can use this to show messages
  about failing to communicate with the server.
• A new error code GIT_EINVALID indicates that an argument to a
  function is invalid, or an invalid operation was requested.
• git_diff_index_to_workdir() and git_diff_tree_to_index() will now
  produce deltas of type GIT_DELTA_CONFLICTED to indicate that the index
  side of the delta is a conflict.
• The git_status family of functions will now produce status of type
  GIT_STATUS_CONFLICTED to indicate that a conflict exists for that file
  in the index.
• git_index_entry_is_conflict() is a utility function to determine if
  a given index entry has a non-zero stage entry, indicating that it is
  one side of a conflict.
• It is now possible to pass a keypair via a buffer instead of a
  path. For this, GIT_CREDTYPE_SSH_MEMORY and
  git_cred_ssh_key_memory_new() have been added.
• git_filter_list_contains will indicate whether a particular
  filter will be run in the given filter list.
• git_commit_header_field() has been added, which allows retrieving
  the contents of an arbitrary header field.
• git_submodule_set_branch() allows to set the configured branch for
  a submodule.

API removals

• git_remote_save() and git_remote_clear_refspecs() have been
  removed. Remote's configuration is changed via the configuration
  directly or through a convenience function which performs changes to
  the configuration directly.
• git_remote_set_callbacks(), git_remote_get_callbacks() and
  git_remote_set_transport() have been removed and the remote no
  longer stores this configuration.
• git_remote_set_fetch_refpecs() and
  git_remote_set_push_refspecs() have been removed. There is no
  longer a way to set the base refspecs at run-time.
• git_submodule_save() has been removed. The submodules are no
  longer configured via the objects.
• git_submodule_reload_all() has been removed as we no longer cache
  submodules.

Breaking API changes

• git_smart_subtransport_cb now has a param parameter.
• The git_merge_options structure member flags has been renamed
  to tree_flags.
• The git_merge_file_options structure member flags is now
  an unsigned int. It was previously a git_merge_file_flags_t.
• GIT_CHECKOUT_SAFE_CREATE has been removed. Most users will generally
  be able to switch to GIT_CHECKOUT_SAFE, but if you require missing
  file handling during checkout, you may now use GIT_CHECKOUT_SAFE | GIT_CHECKOUT_RECREATE_MISSING.
• The git_clone_options and git_submodule_update_options
  structures no longer have a signature field.
• The following functions have removed the signature and/or log message
  parameters in favour of git-emulating ones.
  • git_branch_create(), git_branch_move()
  • git_rebase_init(), git_rebase_abort()
  • git_reference_symbolic_create_matching(),
    git_reference_symbolic_create(), git_reference_create(),
    git_reference_create_matching(),
    git_reference_symbolic_set_target(),
    git_reference_set_target(), git_reference_rename()
  • git_remote_update_tips(), git_remote_fetch(), git_remote_push()
  • git_repository_set_head(),
    git_repository_set_head_detached(),
    git_repository_detach_head()
  • git_reset()
• git_config_get_entry() now gives back a ref-counted
  git_config_entry. You must free it when you no longer need it.
• git_config_get_string() will return an error if used on a
  non-snapshot configuration, as there can be no guarantee that the
  returned pointer is valid.
• git_note_default_ref() now uses a git_buf to return the string,
  as the string is otherwise not guaranteed to stay allocated.
• git_rebase_operation_current() will return GIT_REBASE_NO_OPERATION
  if it is called immediately after creating a rebase session but before
  you have applied the first patch.
• git_rebase_options now contains a git_checkout_options struct
  that will be used for functions that modify the working directory,
  namely git_checkout_init, git_checkout_next and
  git_checkout_abort. As a result, git_rebase_open now also takes
  a git_rebase_options and only the git_rebase_init and
  git_rebase_open functions take a git_rebase_options, where they
  will persist the options to subsequent git_rebase calls.
• The git_clone_options struct now has fetch options in a
  fetch_opts field instead of remote callbacks in
  remote_callbacks.
• The remote callbacks has gained a new member push_negotiation
  which gets called before sending the update commands to the server.
• The following functions no longer act on a remote instance but
  change the repository's configuration. Their signatures have changed
  accordingly:
  • git_remote_set_url(), git_remote_seturl()
  • git_remote_add_fetch(), git_remote_add_push() and
  • git_remote_set_autotag()
• git_remote_connect() and git_remote_prune() now take a pointer
  to the callbacks.
• git_remote_fetch() and git_remote_download() now take a pointer
  to fetch options which determine the runtime configuration.
• The git_remote_autotag_option_t values have been changed. It has
  gained a _UNSPECIFIED default value to specify no override for the
  configured setting.
• git_remote_update_tips() now takes a pointer to the callbacks as
  well as a boolean whether to write FETCH_HEAD and the autotag
  setting.
• git_remote_create_anonymous() no longer takes a fetch refspec as
  url-only remotes cannot have configured refspecs.
• The git_submodule_update_options struct now has fetch options in
  the fetch_opts field instead of callbacks in the
  remote_callbacks field.
• The following functions no longer act on a submodule instance but
  change the repository's configuration. Their signatures have changed
  accordingly:
  • git_submodule_set_url(), git_submodule_set_ignore(),
    git_submodule_set_update(),
    git_submodule_set_fetch_recurse_submodules().
• git_submodule_status() no longer takes a submodule instance but a
  repsitory, a submodule name and an ignore setting.
• The push function in the git_transport interface now takes a
  pointer to the remote callbacks.
• The git_index_entry struct's fields' types have been changed to
  more accurately reflect what is in fact stored in the
  index. Specifically, time and file size are 32 bits intead of 64, as
  these values are truncated.
• GIT_EMERGECONFLICT is now GIT_ECONFLICT, which more accurately
  describes the nature of the error.
• It is no longer allowed to call git_buf_grow() on buffers
  borrowing the memory they point to.