Add changelog for 1.28.0

CHANGELOG.md

@@ -1,5 +1,50 @@
 # Changelog
 
+## [1.28.0] - ?
+
+The new release of rustup has been a long time in the making and comes with substantial changes.
+
+The following improvements might require changes to how you use rustup:
+
+- rustup will no longer automatically install the active toolchain if it is not installed. [pr#3985]
+
+  * To ensure its installation, run `rustup toolchain install` with no arguments.
+  * The following command installs the active toolchain both before and after this change:
+    ```sh
+    rustup show active-toolchain || rustup toolchain install
+    # Or, on older versions of PowerShell:
+    rustup show active-toolchain; if ($LASTEXITCODE -ne 0) { rustup toolchain install }
+    ```
+
+- Installing a host-incompatible toolchain via `rustup toolchain install` or `rustup default` will
+  now be rejected unless you explicitly add the `--force-non-host` flag. [pr#4028]
+
+rustup now officially supports the following host platforms:
+
+  - `aarch64-pc-windows-msvc` [pr#3840]
+  - `loongarch64-unknown-linux-musl` [pr#3921]
+
+We have additionally made the following internal changes:
+
+- The default download backend has been changed from reqwest with native-tls to reqwest with rustls. [pr#3798]
+  - `RUSTUP_USE_CURL` and `RUSTUP_USE_RUSTLS` can still be used to change the download backend
+    if the new backend causes issues.
+  - The default backend now uses rustls-platform-verifier to verify server certificates, taking
+    advantage of the platform's certificate store on platforms that support it. [pr#3903]
+- When creating proxy links, rustup will now try symlinks first and fall back to hardlinks,
+  as opposed to trying hardlinks first. [pr#4023]
+- A new `RUSTUP_LOG` environment variable can be used to control tracing-based logging in
+  rustup binaries. See the [dev guide](https://rust-lang.github.io/rustup/dev-guide/tracing.html) for more details. [pr#3875]
+
+[pr#3985]: https://github.com/rust-lang/rustup/pull/3985
+[pr#4028]: https://github.com/rust-lang/rustup/pull/4028
+[pr#3840]: https://github.com/rust-lang/rustup/pull/3840
+[pr#3921]: https://github.com/rust-lang/rustup/pull/3921
+[pr#3798]: https://github.com/rust-lang/rustup/pull/3798
+[pr#3903]: https://github.com/rust-lang/rustup/pull/3903
+[pr#4023]: https://github.com/rust-lang/rustup/pull/4023
+[pr#3875]: https://github.com/rust-lang/rustup/pull/3875
+
 ## [1.27.1] - 2024-04-14
 
 This new Rustup release involves some minor bug fixes.
@@ -85,7 +130,7 @@ Finally, the project seems to have attracted a total of 23 new contributors with
 
 ### Added
 
-- Add basic support for `fish` shell [pr#3108] 
+- Add basic support for `fish` shell [pr#3108]
 - Add the `RUSTUP_TERM_COLOR` environment variable to force the use of colored output [pr#3435]
 - Improve `rustup-init.sh`'s compatibility with `ksh` and `zsh` [pr#3475]
 - Add a warning when running under Rosetta 2 [pr#3068]