Support modify option names

- New OptionNameModifier which is just a Function<String,String> to
  modify a name.
- Can be defined per option in CommandRegistration.
- Can be defined as global default as bean.
- Default implementation for common case types is enabled via boot's
  config props under spring.shell.option.naming.case-type
- Support facilities for camel, kebab, snake and pascal conversions.
- Fixes #621

spring-shell-docs/src/main/asciidoc/using-shell-commands-programmaticmodel.adoc

@@ -1,3 +1,4 @@
+[[using-shell-commands-programmaticmodel]]
 ==== Programmatic Model
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 

spring-shell-docs/src/main/asciidoc/using-shell-options-naming.adoc

@@ -0,0 +1,113 @@
+[[using-shell-options-naming]]
+=== Naming
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+If there is a need to modify option long names that can be done
+using `OptionNameModifier` interface which is a simple
+`Function<String, String>`. In this interface original option
+name goes in and modified name comes out.
+
+Modifier can be defined per `OptionSpec` in `CommandRegistration`,
+defaulting globally as bean or via configuration properties.
+Modifier defined manually in `OptionSpec` takes takes precedence
+over one defined globally. There is no global modifier defined
+on default.
+
+You can define one with an option in `CommandRegistration`.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/OptionSnippets.java[tag=option-registration-naming-case-req]
+----
+====
+
+Add one _singleton bean_ as type `OptionNameModifier` and that becomes
+a global default.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/OptionSnippets.java[tag=option-registration-naming-case-bean]
+----
+====
+
+It's also possible to just add configuration property with
+`spring.shell.option.naming.case-type` which auto-configures
+one based on a type defined.
+
+`noop` is to do nothing, `camel`, `snake`, `kebab`, `pascal`
+activates build-in modifiers for `camelCase`, `snake_case`,
+`kebab-case` or `PascalCase` respectively.
+
+NOTE: If creating `CommandRegistration` beans directly, global
+default via configuration properies only work if using
+pre-configured `Builder` instance. See more
+<<using-shell-commands-programmaticmodel>>.
+
+====
+[source, yaml]
+----
+spring:
+  shell:
+     option:
+       naming:
+         case-type: noop
+         # case-type: camel
+         # case-type: snake
+         # case-type: kebab
+         # case-type: pascal
+----
+====
+
+For example options defined in an annotated method like this.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/OptionSnippets.java[tag=option-registration-naming-case-sample1]
+----
+====
+
+On default `help` for that command shows names coming
+directly from `@ShellOption`.
+
+====
+[source, bash]
+----
+OPTIONS
+       --from_snake String
+       [Mandatory]
+
+       --fromCamel String
+       [Mandatory]
+
+       --from-kebab String
+       [Mandatory]
+
+       --FromPascal String
+       [Mandatory]
+----
+====
+
+Define `spring.shell.option.naming.case-type=kebab` and default
+modifier is added and option names then look like.
+
+====
+[source, bash]
+----
+OPTIONS
+       --from-snake String
+       [Mandatory]
+
+       --from-camel String
+       [Mandatory]
+
+       --from-kebab String
+       [Mandatory]
+
+       --from-pascal String
+       [Mandatory]
+
+----
+====

spring-shell-docs/src/main/asciidoc/using-shell-options.adoc

@@ -22,3 +22,5 @@ include::using-shell-options-validation.adoc[]
 include::using-shell-options-label.adoc[]
 
 include::using-shell-options-types.adoc[]
+
+include::using-shell-options-naming.adoc[]

spring-shell-docs/src/test/java/org/springframework/shell/docs/OptionSnippets.java

@@ -17,8 +17,11 @@ package org.springframework.shell.docs;
 
 import java.util.Arrays;
 
+import org.springframework.context.annotation.Bean;
 import org.springframework.shell.command.CommandRegistration;
 import org.springframework.shell.command.CommandRegistration.OptionArity;
+import org.springframework.shell.command.CommandRegistration.OptionNameModifier;
+import org.springframework.shell.standard.ShellMethod;
 import org.springframework.shell.standard.ShellOption;
 
 public class OptionSnippets {
@@ -239,6 +242,35 @@ public class OptionSnippets {
 				.and()
 			.build();
 		// end::option-registration-label[]
+
+		// tag::option-registration-naming-case-req[]
+		CommandRegistration.builder()
+			.withOption()
+				.longNames("arg1")
+				.nameModifier(name -> "x" + name)
+				.and()
+			.build();
+		// end::option-registration-naming-case-req[]
+	}
+
+	class Dump8 {
+		// tag::option-registration-naming-case-bean[]
+		@Bean
+		OptionNameModifier sampleOptionNameModifier() {
+			return name -> "x" + name;
+		}
+		// end::option-registration-naming-case-bean[]
+
+		// tag::option-registration-naming-case-sample1[]
+		@ShellMethod(key = "option-naming-sample")
+		public void optionNamingSample(
+			@ShellOption("from_snake") String snake,
+			@ShellOption("fromCamel") String camel,
+			@ShellOption("from-kebab") String kebab,
+			@ShellOption("FromPascal") String pascal
+		) {}
+		// end::option-registration-naming-case-sample1[]
+
 	}
 
 }