Also strip plural "Commands" when inferring command names (#490)

Sometimes a `NoOpCliktCommand` is used to just group further
sub-commands. Such a class may then be called e.g. "ListCommands" with
plural "Commands". Support stripping that suffix for such cases.

clikt/src/commonMain/kotlin/com/github/ajalt/clikt/core/CliktCommand.kt

@@ -539,8 +539,14 @@ private fun Any.classSimpleName(): String = this::class.simpleName.orEmpty().spl
 
 private fun CliktCommand.inferCommandName(): String {
     val name = classSimpleName()
-    if (name == "Command") return "command"
-    return name.removeSuffix("Command").replace(Regex("([a-z])([A-Z])")) {
+
+    val suffixes = setOf("Command", "Commands")
+    if (name in suffixes) return name.lowercase()
+
+    val nameWithoutSuffixes = suffixes.fold(name) { acc, s -> acc.removeSuffix(s) }
+    val lowerUpperRegex = Regex("([a-z])([A-Z])")
+
+    return nameWithoutSuffixes.replace(lowerUpperRegex) {
         "${it.groupValues[1]}-${it.groupValues[2]}"
     }.lowercase()
 }

clikt/src/commonTest/kotlin/com/github/ajalt/clikt/core/CliktCommandTest.kt

@@ -6,7 +6,6 @@ import com.github.ajalt.clikt.parameters.groups.OptionGroup
 import com.github.ajalt.clikt.parameters.groups.cooccurring
 import com.github.ajalt.clikt.parameters.groups.mutuallyExclusiveOptions
 import com.github.ajalt.clikt.parameters.groups.provideDelegate
-import com.github.ajalt.clikt.parameters.options.defaultLazy
 import com.github.ajalt.clikt.parameters.options.flag
 import com.github.ajalt.clikt.parameters.options.option
 import com.github.ajalt.clikt.parameters.options.required
@@ -35,9 +34,11 @@ class CliktCommandTest {
         class ListAllValuesCommand : TestCommand()
         class LGTMMeansLookingGoodToMe : TestCommand()
         class `nothing-to-change` : TestCommand()
+        class ListCommands : NoOpCliktCommand()
         ListAllValuesCommand().commandName shouldBe "list-all-values"
         LGTMMeansLookingGoodToMe().commandName shouldBe "lgtmmeans-looking-good-to-me"
         `nothing-to-change`().commandName shouldBe "nothing-to-change"
+        ListCommands().commandName shouldBe "list"
     }
 
     @Test