CHANGELOG: add initial changelog with current history

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

CHANGELOG.md

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+# Changelog #
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased] ##
+
+### Changed ###
+- By allowing `Open(at)InRoot` to opt-out of the extra work done by `MkdirAll`
+  to do the necessary "partial lookups", `Open(at)InRoot` now does less work
+  for both implementations (resulting in a many-fold decrease in the number of
+  operations for `openat2`, and a modest improvement for non-`openat2`) and is
+  far more guaranteed to match the correct `openat2(RESOLVE_IN_ROOT)`
+  behaviour.
+
+### Fixed ###
+- Several improvements were made to the errors returned by `Open(at)InRoot` and
+  `MkdirAll` when dealing with invalid paths under the emulated (ie.
+  non-`openat2`) implementation. Previously, some paths would return the wrong
+  error (`ENOENT` when the last component was a non-directory), and other paths
+  would be returned as though they were acceptable (trailing-slash components
+  after a non-directory would be ignored by `Open(at)InRoot`).
+
+  These changes were done to match `openat2`'s behaviour and purely is a
+  consistency fix (most users are going to be using `openat2` anyway).
+
+## [0.3.0] - 2024-07-11 ##
+
+### Added ###
+- A new set of `*os.File`-based APIs have been added. These are adapted from
+  [libpathrs][] and we strongly suggest using them if possible (as they provide
+  far more protection against attacks than `SecureJoin`):
+
+   - `Open(at)InRoot` resolves a path inside a rootfs and returns an `*os.File`
+     handle to the path. Note that the handle returned is an `O_PATH` handle,
+     which cannot be used for reading or writing (as well as some other
+     operations -- [see open(2) for more details][open.2])
+
+   - `Reopen` takes an `O_PATH` file handle and safely re-opens it to upgrade
+     it to a regular handle. This can also be used with non-`O_PATH` handles,
+     but `O_PATH` is the most obvious application.
+
+   - `MkdirAll` is an implementation of `os.MkdirAll` that is safe to use to
+     create a directory tree within a rootfs.
+
+  As these are new APIs, they may change in the future. However, they should be
+  safe to start migrating to as we have extensive tests ensuring they behave
+  correctly and are safe against various races and other attacks.
+
+[libpathrs]: https://github.com/openSUSE/libpathrs
+[open.2]: https://www.man7.org/linux/man-pages/man2/open.2.html
+
+## [0.2.5] - 2024-05-03 ##
+
+### Changed ###
+- Some minor changes were made to how lexical components (like `..` and `.`)
+  are handled during path generation in `SecureJoin`. There is no behaviour
+  change as a result of this fix (the resulting paths are the same).
+
+### Fixed ###
+- The error returned when we hit a symlink loop now references the correct
+  path. (#10)
+
+## [0.2.4] - 2023-09-06 ##
+
+### Security ###
+- This release fixes a potential security issue in filepath-securejoin when
+  used on Windows ([GHSA-6xv5-86q9-7xr8][], which could be used to generate
+  paths outside of the provided rootfs in certain cases), as well as improving
+  the overall behaviour of filepath-securejoin when dealing with Windows paths
+  that contain volume names. Thanks to Paulo Gomes for discovering and fixing
+  these issues.
+
+### Fixed ###
+- Switch to GitHub Actions for CI so we can test on Windows as well as Linux
+  and MacOS.
+
+[GHSA-6xv5-86q9-7xr8]: https://github.com/advisories/GHSA-6xv5-86q9-7xr8
+
+## [0.2.3] - 2021-06-04 ##
+
+### Changed ###
+- Switch to Go 1.13-style `%w` error wrapping, letting us drop the dependency
+  on `github.com/pkg/errors`.
+
+## [0.2.2] - 2018-09-05 ##
+
+### Changed ###
+- Use `syscall.ELOOP` as the base error for symlink loops, rather than our own
+  (internal) error. This allows callers to more easily use `errors.Is` to check
+  for this case.
+
+## [0.2.1] - 2018-09-05 ##
+
+### Fixed ###
+- Use our own `IsNotExist` implementation, which lets us handle `ENOTDIR`
+  properly within `SecureJoin`.
+
+## [0.2.0] - 2017-07-19 ##
+
+We now have 100% test coverage!
+
+### Added ###
+- Add a `SecureJoinVFS` API that can be used for mocking (as we do in our new
+  tests) or for implementing custom handling of lookup operations (such as for
+  rootless containers, where work is necessary to access directories with weird
+  modes because we don't have `CAP_DAC_READ_SEARCH` or `CAP_DAC_OVERRIDE`).
+
+## 0.1.0 - 2017-07-19
+
+This is our first release of `github.com/cyphar/filepath-securejoin`,
+containing a full implementation with a coverage of 93.5% (the only missing
+cases are the error cases, which are hard to mocktest at the moment).
+
+[Unreleased]: https://github.com/cyphar/filepath-securejoin/compare/v0.3.0...HEAD
+[0.3.0]: https://github.com/cyphar/filepath-securejoin/compare/v0.2.5...v0.3.0
+[0.2.5]: https://github.com/cyphar/filepath-securejoin/compare/v0.2.4...v0.2.5
+[0.2.4]: https://github.com/cyphar/filepath-securejoin/compare/v0.2.3...v0.2.4
+[0.2.3]: https://github.com/cyphar/filepath-securejoin/compare/v0.2.2...v0.2.3
+[0.2.2]: https://github.com/cyphar/filepath-securejoin/compare/v0.2.1...v0.2.2
+[0.2.1]: https://github.com/cyphar/filepath-securejoin/compare/v0.2.0...v0.2.1
+[0.2.0]: https://github.com/cyphar/filepath-securejoin/compare/v0.1.0...v0.2.0