Bump version to v1.2.1.

CHANGELOG.md

@@ -10,11 +10,16 @@ The format is based on [Keep a Changelog], and this project adheres to
 [keep a changelog]: https://keepachangelog.com/en/1.0.0/
 [semantic versioning]: https://semver.org/spec/v2.0.0.html
 
-## [Unreleased]
+## [1.2.1] - 2023-08-14
 
 ### Changed
 
 - Dropped support for Go v1.19, which reached end-of-life on 2023-08-08
+- Removed use of the `slices` and `maps` packages from `golang.org/x/exp`. These
+  package are not versioned and as such breaking changes can cause conflicts
+  with other dependencies. The experimental `constraints` package is still used,
+  with the expectation that these will always remain valid for use as type
+  parameter constraints.
 
 ## [1.2.0] - 2023-06-12
 
@@ -256,6 +261,7 @@ The two most important changes in usage are:
 [1.0.3]: https://github.com/dogmatiq/ferrite/releases/tag/v1.0.3
 [1.1.0]: https://github.com/dogmatiq/ferrite/releases/tag/v1.1.0
 [1.2.0]: https://github.com/dogmatiq/ferrite/releases/tag/v1.2.0
+[1.2.1]: https://github.com/dogmatiq/ferrite/releases/tag/v1.2.1
 
 <!-- version template
 ## [0.0.1] - YYYY-MM-DD

option_relevantif.go

@@ -12,7 +12,7 @@ import (
 // A "irrelevant" variable set behaves as though its environment variables are
 // undefined, irrespective of the actual values of the variables and any default
 // values.
-func RelevantIf(s VariableSet, options ...RelevantIfOption) interface {
+func RelevantIf(s VariableSet, _ ...RelevantIfOption) interface {
 	RequiredOption
 	OptionalOption
 	DeprecatedOption

option_seealso.go

@@ -4,7 +4,7 @@ import "github.com/dogmatiq/ferrite/internal/variable"
 
 // SeeAlso is an option for a variable set that adds the variables in another
 // set, s, to the "see also" section of the generated documentation.
-func SeeAlso(s VariableSet, options ...SeeAlsoOption) interface {
+func SeeAlso(s VariableSet, _ ...SeeAlsoOption) interface {
 	RequiredOption
 	OptionalOption
 	DeprecatedOption

option_supersede.go

@@ -4,7 +4,7 @@ import "github.com/dogmatiq/ferrite/internal/variable"
 
 // SupersededBy is a option for a deprecated variable set that indicates the
 // variables in another set, s, should be used instead.
-func SupersededBy(s VariableSet, options ...SupersededByOption) DeprecatedOption {
+func SupersededBy(s VariableSet, _ ...SupersededByOption) DeprecatedOption {
 	return option{
 		ApplyToSpecInDeprecatedSet: func(b variable.SpecBuilder) {
 			for _, v := range s.variables() {