Tweak documentation adding more references to the set notation

Cabal/doc/developing-packages.rst

@@ -1104,7 +1104,23 @@ describe the package as a whole:
 .. pkg-field:: tested-with: compiler list
 
     A list of compilers and versions against which the package has been
-    tested (or at least built).
+    tested (or at least built). The value of this field is not used by Cabal
+    and is rather intended as extra metadata for use by third party
+    tooling, such as e.g. CI tooling.
+
+    Here's a typical usage example
+
+    ::
+
+        tested-with: GHC == 8.6.3, GHC == 8.4.4, GHC == 8.2.2, GHC == 8.0.2,
+                     GHC == 7.10.3, GHC == 7.8.4, GHC == 7.6.3, GHC == 7.4.2
+
+    which can (starting with Cabal 3.0) also be written using the more
+    concise set notation syntax
+
+    ::
+
+        tested-with: GHC == { 8.6.3, 8.4.4, 8.2.2, 8.0.2, 7.10.3, 7.8.4, 7.6.3, 7.4.2 }
 
 .. pkg-field:: data-files: filename list
 

Cabal/doc/file-format-changelog.rst

@@ -55,6 +55,9 @@ relative to the respective preceding *published* version.
   name(s) must be of the form `lib<library-name>.<dyn-library-extension>*`
   instead of the old `libC<library-name>-ghc<ghc-flavour><ghc-version>.<dyn-library-extension>`
 
+* New set-notation syntax for ``==`` and ``^>=`` operators, see
+  :pkg-field:`build-depends` field documentation for examples.
+
 ``cabal-version: 2.4``
 ----------------------