v0.26.8

-------

This as a security release fixing the following list of issues:

- The function family `git__strtol` is used to parse integers

  from a buffer. As the functions do not take a buffer length as

  argument, they will scan either until the end of the current

  number or until a NUL byte is encountered. Many callers have

  been misusing the function and called it on potentially

  non-NUL-terminated buffers, resulting in possible out-of-bounds

  reads. Callers have been fixed to use `git__strntol` functions

  instead and `git__strtol` functions were removed.

- The function `git__strntol64` relied on the undefined behavior

  of signed integer overflows. While the code tried to detect

  such overflows after they have happened, this is unspecified

  behavior and may lead to weird behavior on uncommon platforms.

- In the case where `git__strntol32` was unable to parse an

  integer because it doesn't fit into an `int32_t`, it printed an

  error message containing the string that is currently being

  parsed. The code didn't truncate the string though, which

  caused it to print the complete string until a NUL byte is

  encountered and not only the currently parsed number. In case

  where the string was not NUL terminated, this could have lead

  to an out-of-bounds read.

- When parsing tags, all unknown fields that appear before the

  tag message are skipped. This skipping is done by using a plain

  `strstr(buffer, "\n\n")` to search for the two newlines that

  separate tag fields from tag message. As it is not possible to

  supply a buffer length to `strstr`, this call may skip over the

  buffer's end and thus result in an out of bounds read. As

  `strstr` may return a pointer that is out of bounds, the

  following computation of `buffer_end - buffer` will overflow

  and result in an allocation of an invalid length. Note that

  when reading objects from the object database, we make sure to

  always NUL terminate them, making the use of `strstr` safe.

- When parsing the "encoding" field of a commit, we may perform

  an out of bounds read due to using `git__prefixcmp` instead of

  `git__prefixncmp`. This can result in the parsed commit object

  containing uninitialized data in both its message encoding and

  message fields. Note that when reading objects from the object

  database, we make sure to always NUL terminate them, making the

  use of `strstr` safe.

v0.26.7

-------

This is a security release fixing the following list of issues:

- Submodule URLs and paths with a leading "-" are now ignored.

  This is due to the recently discovered CVE-2018-17456, which

  can lead to arbitrary code execution in upstream git. While

  libgit2 itself is not vulnerable, it can be used to inject

  options in an implementation which performs a recursive clone

  by executing an external command.

- When running repack while doing repo writes,

  `packfile_load__cb()` could see some temporary files in the

  directory that were bigger than the usual, and makes `memcmp`

  overflow on the `p->pack_name` string. This issue was reported

  and fixed by bisho.

- The configuration file parser used unbounded recursion to parse

  multiline variables, which could lead to a stack overflow. The

  issue was reported by the oss-fuzz project, issue 10048 and

  fixed by Nelson Elhage.

- The fix to the unbounded recursion introduced a memory leak in

  the config parser. While this leak was never in a public

  release, the oss-fuzz project reported this as issue 10127. The

  fix was implemented by Nelson Elhage and Patrick Steinhardt.

- When parsing "ok" packets received via the smart protocol, our

  parsing code did not correctly verify the bounds of the

  packets, which could result in a heap-buffer overflow. The

  issue was reported by the oss-fuzz project, issue 9749 and

  fixed by Patrick Steinhardt.

- The parsing code for the smart protocol has been tightened in

  general, fixing heap-buffer overflows when parsing the packet

  type as well as for "ACK" and "unpack" packets. The issue was

  discovered and fixed by Patrick Steinhardt.

- Fixed potential integer overflows on platforms with 16 bit

  integers when parsing packets for the smart protocol. The issue

  was discovered and fixed by Patrick Steinhardt.

- Fixed potential NULL pointer dereference when parsing

  configuration files which have "include.path" statements

  without a value.

v0.26.6

-------

This is a security release fixing out-of-bounds reads when

processing smart-protocol "ng" packets.

When parsing an "ng" packet, we keep track of both the current position

as well as the remaining length of the packet itself. But instead of

taking care not to exceed the length, we pass the current pointer's

position to `strchr`, which will search for a certain character until

hitting NUL. It is thus possible to create a crafted packet which

doesn't contain a NUL byte to trigger an out-of-bounds read.

The issue was discovered by the oss-fuzz project, issue 9406.

v0.26.5

-------

This is a security release fixing out-of-bounds reads when

reading objects from a packfile. This corresponds to

CVE-2018-10887 and CVE-2018-10888, which were both reported by

Riccardo Schirone.

When packing objects into a single so-called packfile, objects

may not get stored as complete copies but instead as deltas

against another object "base". A specially crafted delta object

could trigger an integer overflow and thus bypass our input

validation, which may result in copying memory before or after

the base object into the final deflated object. This may lead to

objects containing copies of system memory being written into the

object database. As the hash of those objects cannot be easily

controlled by the attacker, it is unlikely that any of those

objects will be valid and referenced by the commit graph.

Note that the error could also be triggered by the function

`git_apply__patch`. But as this function is not in use outside of

our test suite, it is not a possible attack vector.

v0.26.4

-------

This is a security release fixing insufficient validation of submodule names

(CVE-2018-11235, reported by Etienne Stalmans) and disallows `.gitmodules` files

as symlinks.

While submodule names come from the untrusted ".gitmodules" file, we blindly

append the name to "$GIT_DIR/modules" to construct the final path of the

submodule repository. In case the name contains e.g. "../", an adversary would

be able to escape your repository and write data at arbitrary paths. In

accordance with git, we now enforce some rules for submodule names which will

cause libgit2 to ignore these malicious names.

Adding a symlink as `.gitmodules` into the index from the workdir or checking

out such files is not allowed as this can make a Git implementation write

outside of the repository and bypass the `fsck` checks for CVE-2018-11235.

libgit2 is not susceptible to CVE-2018-11233.

v0.26.3

-------

This is a bugfix release. It includes the following non-exclusive list of

improvements, which have been backported from the master branch:

* Fix cloning of the libgit2 project with `git clone --recursive` by removing an

  invalid submodule from our testing data.

* Fix endianness of the port in `p_getaddrinfo()`.

* Fix handling of negative gitignore rules with wildcards.

* Fix handling of case-insensitive negative gitignore rules.

* Fix resolving references to a tag if the reference is stored with its fully

  resolved OID in the packed-refs file.

* Fix checkout not treating worktree files as modified when only their mode has

  changed.

* Fix rename detection with `GIT_DIFF_FIND_RENAMES_FROM_REWRITES`.

* Enable Windows 7 and earlier to use TLS 1.2.

v0.26.2

-------

This is a security release fixing memory handling issues when reading crafted

repository index files. The issues allow for possible denial of service due to

allocation of large memory and out-of-bound reads.

As the index is never transferred via the network, exploitation requires an

attacker to have access to the local repository.

v0.26.1

---------

This is a security release fixing the following CVEs in the bundled zlib

library:

* CVE-2016-9843

* CVE-2016-9841

* CVE-2016-9842

* CVE-2016-9840

All users compiling libgit2 with the bundled zlib instead of using the

system-provided zlib must upgrade.

v0.26

-----

### Changes or improvements

* Support for opening, creating and modifying worktrees.

* We can now detect SHA1 collisions resulting from the SHAttered attack. These

  checks can be enabled at build time via `-DUSE_SHA1DC`.

* Fix for missing implementation of `git_merge_driver_source` getters.

* Fix for installed pkg-config file being broken when the prefix contains

  spaces.

* We now detect when the hashsum of on-disk objects does not match their

  expected hashsum.

* We now support open-ended ranges (e.g. "master..", "...master") in our

  revision range parsing code.

* We now correctly compute ignores with leading "/" in subdirectories.

* We now optionally call `fsync` on loose objects, packfiles and their indexes,

  loose references and packed reference files.

* We can now build against OpenSSL v1.1 and against LibreSSL.

* `GIT_MERGE_OPTIONS_INIT` now includes a setting to perform rename detection.

  This aligns this structure with the default by `git_merge` and

  `git_merge_trees` when `NULL` was provided for the options.

* Improvements for reading index v4 files.

* Perform additional retries for filesystem operations on Windows when files

  are temporarily locked by other processes.

### API additions

* New family of functions to handle worktrees:

    * `git_worktree_list()` lets you look up worktrees for a repository.

    * `git_worktree_lookup()` lets you get a specific worktree.

    * `git_worktree_open_from_repository()` lets you get the associated worktree

      of a repository.

      a worktree.

    * `git_worktree_add` lets you create new worktrees.

    * `git_worktree_prune` lets you remove worktrees from disk.

    * `git_worktree_lock()` and `git_worktree_unlock()` let you lock

      respectively unlock a worktree.

    * `git_repository_open_from_worktree()` lets you open a repository via

    * `git_repository_head_for_worktree()` lets you get the current `HEAD` for a

      linked worktree.

    * `git_repository_head_detached_for_worktree()` lets you check whether a

      linked worktree is in detached HEAD mode.

* `git_repository_item_path()` lets you retrieve paths for various repository

  files.

* `git_repository_commondir()` lets you retrieve the common directory of a

  repository.

* `git_branch_is_checked_out()` allows you to check whether a branch is checked

  out in a repository or any of its worktrees.

* `git_repository_submodule_cache_all()` and

  `git_repository_submodule_cache_clear()` functions allow you to prime or clear

  the submodule cache of a repository.

* You can disable strict hash verifications via the

  `GIT_OPT_ENABLE_STRICT_HASH_VERIFICATION` option with `git_libgit2_opts()`.

* You can enable us calling `fsync` for various files inside the ".git"

  directory by setting the `GIT_OPT_ENABLE_FSYNC_GITDIR` option with

  `git_libgit2_opts()`.

* You can now enable "offset deltas" when creating packfiles and negotiating

  packfiles with a remote server by setting `GIT_OPT_ENABLE_OFS_DELTA` option

  with `GIT_libgit2_opts()`.

* You can now set the default share mode on Windows for opening files using

  `GIT_OPT_SET_WINDOWS_SHAREMODE` option with `git_libgit2_opts()`.

  You can query the current share mode with `GIT_OPT_GET_WINDOWS_SHAREMODE`.

* `git_transport_smart_proxy_options()' enables you to get the proxy options for

  smart transports.

* The `GIT_FILTER_INIT` macro and the `git_filter_init` function are provided

  to initialize a `git_filter` structure.

### Breaking API changes

* `clone_checkout_strategy` has been removed from

  `git_submodule_update_option`. The checkout strategy used to clone will

  be the same strategy specified in `checkout_opts`.

v0.25

-------

### Changes or improvements

* Fix repository discovery with `git_repository_discover` and

  `git_repository_open_ext` to match git's handling of a ceiling

  directory at the current directory. git only checks ceiling

  directories when its search ascends to a parent directory.  A ceiling

  directory matching the starting directory will not prevent git from

  finding a repository in the starting directory or a parent directory.

* Do not fail when deleting remotes in the presence of broken

  global configs which contain branches.

* Support for reading and writing git index v4 files

* Improve the performance of the revwalk and bring us closer to git's code.

* The reference db has improved support for concurrency and returns `GIT_ELOCKED`

  when an operation could not be performed due to locking.

* Nanosecond resolution is now activated by default, following git's change to

  do this.

* We now restrict the set of ciphers we let OpenSSL use by default.

* Users can now register their own merge drivers for use with `.gitattributes`.

  The library also gained built-in support for the union merge driver.

* The default for creating references is now to validate that the object does

  exist.

* Add `git_proxy_options` which is used by the different networking

  implementations to let the caller specify the proxy settings instead of

  relying on the environment variables.

### API additions

* You can now get the user-agent used by libgit2 using the

  `GIT_OPT_GET_USER_AGENT` option with `git_libgit2_opts()`.

  It is the counterpart to `GIT_OPT_SET_USER_AGENT`.

* The `GIT_OPT_SET_SSL_CIPHERS` option for `git_libgit2_opts()` lets you specify

  a custom list of ciphers to use for OpenSSL.

* `git_commit_create_buffer()` creates a commit and writes it into a

  user-provided buffer instead of writing it into the object db. Combine it with

  `git_commit_create_with_signature()` in order to create a commit with a

  cryptographic signature.

* `git_blob_create_fromstream()` and

  `git_blob_create_fromstream_commit()` allow you to create a blob by

  writing into a stream. Useful when you do not know the final size or

  want to copy the contents from another stream.

* New flags for `git_repository_open_ext`:

    * `GIT_REPOSITORY_OPEN_NO_DOTGIT` - Do not check for a repository by

      appending `/.git` to the `start_path`; only open the repository if

      `start_path` itself points to the git directory.

    * `GIT_REPOSITORY_OPEN_FROM_ENV` - Find and open a git repository,

      respecting the environment variables used by the git command-line

      tools. If set, `git_repository_open_ext` will ignore the other

      flags and the `ceiling_dirs` argument, and will allow a NULL

      `path` to use `GIT_DIR` or search from the current directory. The

      search for a repository will respect `$GIT_CEILING_DIRECTORIES`

      and `$GIT_DISCOVERY_ACROSS_FILESYSTEM`.  The opened repository

      will respect `$GIT_INDEX_FILE`, `$GIT_NAMESPACE`,

      `$GIT_OBJECT_DIRECTORY`, and `$GIT_ALTERNATE_OBJECT_DIRECTORIES`.

      In the future, this flag will also cause `git_repository_open_ext`

      to respect `$GIT_WORK_TREE` and `$GIT_COMMON_DIR`; currently,

      `git_repository_open_ext` with this flag will error out if either

      `$GIT_WORK_TREE` or `$GIT_COMMON_DIR` is set.

* `git_diff_from_buffer()` can create a `git_diff` object from the contents

  of a git-style patch file.

* `git_index_version()` and `git_index_set_version()` to get and set

  the index version

* `git_odb_expand_ids()` lets you check for the existence of multiple

  objects at once.

* The new `git_blob_dup()`, `git_commit_dup()`, `git_tag_dup()` and

  `git_tree_dup()` functions provide type-specific wrappers for

  `git_object_dup()` to reduce noise and increase type safety for callers.

* `git_reference_dup()` lets you duplicate a reference to aid in ownership

  management and cleanup.

* `git_signature_from_buffer()` lets you create a signature from a string in the

  format that appear in objects.

* `git_tree_create_updated()` lets you create a tree based on another one

  together with a list of updates. For the covered update cases, it's more

  efficient than the `git_index` route.

* `git_apply_patch()` applies hunks from a `git_patch` to a buffer.

* `git_diff_to_buf()` lets you print an entire diff directory to a buffer,

  similar to how `git_patch_to_buf()` works.

* `git_proxy_init_options()` is added to initialize a `git_proxy_options`

  structure at run-time.

* `git_merge_driver_register()`, `git_merge_driver_unregister()` let you

  register and unregister a custom merge driver to be used when `.gitattributes`

  specifies it.

* `git_merge_driver_lookup()` can be used to look up a merge driver by name.

* `git_merge_driver_source_repo()`, `git_merge_driver_source_ancestor()`,

  `git_merge_driver_source_ours()`, `git_merge_driver_source_theirs()`,

  `git_merge_driver_source_file_options()` added as accessors to

  `git_merge_driver_source`.

### API removals

* `git_blob_create_fromchunks()` has been removed in favour of

  `git_blob_create_fromstream()`.

### Breaking API changes

* `git_packbuilder_object_count` and `git_packbuilder_written` now

  return a `size_t` instead of a `uint32_t` for more thorough

  compatibility with the rest of the library.

* `git_packbuiler_progress` now provides explicitly sized `uint32_t`

  values instead of `unsigned int`.

* `git_diff_file` now includes an `id_abbrev` field that reflects the

  number of nibbles set in the `id` field.

* `git_odb_backend` now has a `freshen` function pointer.  This optional

  function pointer is similar to the `exists` function, but it will update

  a last-used marker.  For filesystem-based object databases, this updates

  the timestamp of the file containing the object, to indicate "freshness".

  If this is `NULL`, then it will not be called and the `exists` function

  will be used instead.

* `git_remote_connect()` now accepts `git_proxy_options` argument, and

  `git_fetch_options` and `git_push_options` each have a `proxy_opts` field.

* `git_merge_options` now provides a `default_driver` that can be used

  to provide the name of a merge driver to be used to handle files changed

  during a merge.

v0.24

-------

### Changes or improvements

* Custom merge drivers can now be registered, which allows callers to

  configure callbacks to honor `merge=driver` configuration in

  `.gitattributes`.

* Custom filters can now be registered with wildcard attributes, for

  example `filter=*`.  Consumers should examine the attributes parameter

  of the `check` function for details.

* Symlinks are now followed when locking a file, which can be

  necessary when multiple worktrees share a base repository.

* You can now set your own user-agent to be sent for HTTP requests by

  using the `GIT_OPT_SET_USER_AGENT` with `git_libgit2_opts()`.

* You can set custom HTTP header fields to be sent along with requests

  by passing them in the fetch and push options.

* Tree objects are now assumed to be sorted. If a tree is not

  correctly formed, it will give bad results. This is the git approach

  and cuts a significant amount of time when reading the trees.

* Filter registration is now protected against concurrent

  registration.

* Filenames which are not valid on Windows in an index no longer cause

  to fail to parse it on that OS.

* Rebases can now be performed purely in-memory, without touching the

  repository's workdir.

* When adding objects to the index, or when creating new tree or commit

  objects, the inputs are validated to ensure that the dependent objects

  exist and are of the correct type.  This object validation can be

  disabled with the GIT_OPT_ENABLE_STRICT_OBJECT_CREATION option.

* The WinHTTP transport's handling of bad credentials now behaves like

  the others, asking for credentials again.

### API additions

* `git_config_lock()` has been added, which allow for

  transactional/atomic complex updates to the configuration, removing

  the opportunity for concurrent operations and not committing any

  changes until the unlock.

* `git_diff_options` added a new callback `progress_cb` to report on the

  progress of the diff as files are being compared. The documentation of

  the existing callback `notify_cb` was updated to reflect that it only

  gets called when new deltas are added to the diff.

* `git_fetch_options` and `git_push_options` have gained a `custom_headers`

  field to set the extra HTTP header fields to send.

* `git_stream_register_tls()` lets you register a callback to be used

  as the constructor for a TLS stream instead of the libgit2 built-in

  one.

* `git_commit_header_field()` allows you to look up a specific header

  field in a commit.

* `git_commit_extract_signature()` extracts the signature from a

  commit and gives you both the signature and the signed data so you

  can verify it.

### API removals

* No APIs were removed in this version.

### Breaking API changes

* The `git_merge_tree_flag_t` is now `git_merge_flag_t`.  Subsequently,

  its members are no longer prefixed with `GIT_MERGE_TREE_FLAG` but are

  now prefixed with `GIT_MERGE_FLAG`, and the `tree_flags` field of the

  `git_merge_options` structure is now named `flags`.

* The `git_merge_file_flags_t` enum is now `git_merge_file_flag_t` for

  consistency with other enum type names.

* `git_cert` descendent types now have a proper `parent` member

* It is the responsibility of the refdb backend to decide what to do

  with the reflog on ref deletion. The file-based backend must delete

  it, a database-backed one may wish to archive it.

* `git_config_backend` has gained two entries. `lock` and `unlock`

  with which to implement the transactional/atomic semantics for the

  configuration backend.

* `git_index_add` and `git_index_conflict_add()` will now use the case

  as provided by the caller on case insensitive systems.  Previous

  versions would keep the case as it existed in the index.  This does

  not affect the higher-level `git_index_add_bypath` or

  `git_index_add_frombuffer` functions.

* The `notify_payload` field of `git_diff_options` was renamed to `payload`

  to reflect that it's also the payload for the new progress callback.

* The `git_config_level_t` enum has gained a higher-priority value

  `GIT_CONFIG_LEVEL_PROGRAMDATA` which represent a rough Windows equivalent

  to the system level configuration.

* `git_rebase_options` now has a `merge_options` field.

* The index no longer performs locking itself. This is not something

  users of the library should have been relying on as it's not part of

  the concurrency guarantees.

* `git_remote_connect()` now takes a `custom_headers` argument to set

  the extra HTTP header fields to send.

v0.23

------

### 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_rebase_init`, `git_rebase_next` and

  `git_rebase_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.

v0.22

------

### Changes or improvements

* `git_signature_new()` now requires a non-empty email address.

* Use CommonCrypto libraries for SHA-1 calculation on Mac OS X.

* Disable SSL compression and SSLv2 and SSLv3 ciphers in favor of TLSv1

  in OpenSSL.

* The fetch behavior of remotes with autotag set to `GIT_REMOTE_DOWNLOAD_TAGS_ALL`

  has been changed to match git 1.9.0 and later. In this mode, libgit2 now

  fetches all tags in addition to whatever else needs to be fetched.

* `git_checkout()` now handles case-changing renames correctly on

  case-insensitive filesystems; for example renaming "readme" to "README".

* The search for libssh2 is now done via pkg-config instead of a