For example, if we follow the links from the downloads page for the 5.4.2 release we end up on this page. The release notes there are:
swift-5.4.2-RELEASE
Change version string to 'swift-5.4.2-RELEASE'
Which is not very helpful for developers that are looking to get information about the actual changes associated with a swift release.
An updated changelog is maintained in swift/CHANGELOG.md at main · apple/swift · GitHub.
Thank you very much for providing that link. I will definitely keep it around for the future. However, that document does not distinguish based on point releases like 5.4.2.
These point releases are specific to Linux and Windows. They contain bug fixes and incremental implementations of the missing functionality in Swift core libraries. They do not change compiler or any language features. See this post that started these releases: Announcing Swift 4.2.2 and monthly Swift 4.2.x dot releases for Linux
If a release includes an important fix (such as a security fix) the forum release announcement will mention it.
I know that normally the point releases are linux or windows specific, however I found it interesting that 5.4.2 was noted to be included as part of Xcode 12.5.1 which is different than most other point releases (usually they not that they are windows/linux specific and are not present in an Xcode update).
This usually indicates that an updated version of swift-corelibs-xctest is included with Xcode.
Forgot to mention two things:
First, there are more projects that are part of Swift distribution that get these interim fixes, including SPM, swift-llbuild, swift-xcode-playground-support and a few more.
Second, these changes are found in Xcode release notes. In this case, 12.5.1, which happens to update XCTest and SPM.