Update docs

spring-shell-docs/modules/ROOT/pages/customization/commandnotfound.adoc

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+[[using-shell-customization-commandnotfound]]
+= Command Not Found
+
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+On default a missing command is handled via `CommandNotFoundResultHandler`
+and outputs a simple message:
+
+[source, text]
+----
+shell:>missing
+No command found for 'missing'
+----
+
+Internally `CommandNotFoundResultHandler` is using `CommandNotFoundMessageProvider`
+which is a simple function taking a `ProviderContext` and returning a text
+message. Below is an example what a custom message provider might look like.
+
+[source, java, indent=0]
+----
+include::{snippets}/CommandNotFoundSnippets.java[tag=custom-provider]
+----
+
+It's possible to change this implementation by defining it as a bean.
+
+[source, java, indent=0]
+----
+include::{snippets}/CommandNotFoundSnippets.java[tag=provider-bean-1]
+----
+
+`CommandNotFoundResultHandler` is a functional interface so it can
+be writter as a lambda.
+
+[source, java, indent=0]
+----
+include::{snippets}/CommandNotFoundSnippets.java[tag=provider-bean-2]
+----

spring-shell-docs/modules/ROOT/pages/customization/contextclose.adoc

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+[[using-shell-customization-contextclose]]
+= Context Close
+:page-section-summary-toc: 1
+
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Command execution logic happens via Spring Boot's `ApplicationRunner` beans.
+Normally Spring `ApplicationContext` closes automatically after these runner
+beans has been processed unless there is something what keeps it alive like
+use of `@EnableScheduling` or generally speaking there are threads which
+don't die automatically.
+
+It is possible to add configuration property `spring.shell.context.close`
+which registers `ApplicationListener` for `ApplicationReadyEvent` and requests
+context close after shell has completed its execution logic.
+
+[source, yaml]
+----
+spring:
+  shell:
+    context:
+      close: true
+----
+
+NOTE: This setting is not enabled by default.

spring-shell-docs/modules/ROOT/pages/customization/index.adoc

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+[[using-shell-customization]]
+= Customization
+:page-section-summary-toc: 1
+
+This section describes how you can customize the shell.
+
+
+
+

spring-shell-docs/modules/ROOT/pages/customization/logging.adoc

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+[[using-shell-customization-logging]]
+= Logging
+
+On default a _Spring Boot_ application will log messages into a console which
+at minimum is annoying and may also mix output from a shell commands.
+Fortunately there is a simple way to instruct logging changes via boot properties.
+
+Completely silence console logging by defining its pattern as an empty value.
+
+[source, yaml]
+----
+logging:
+  pattern:
+    console:
+----
+
+If you need log from a shell then write those into a file.
+
+[source, yaml]
+----
+logging:
+  file:
+    name: shell.log
+----
+
+If you need different log levels.
+
+[source, yaml]
+----
+logging:
+  level:
+    org:
+      springframework:
+        shell: debug
+----
+
+Passing contiguration properties as command line options is not supported but
+you can use any other ways supported by boot, for example.
+
+[source, bash]
+----
+$ java -Dlogging.level.root=debug -jar demo.jar
+$ LOGGING_LEVEL_ROOT=debug java -jar demo.jar
+----
+
+NOTE: In a GraalVM image settings are locked during compilation which means
+      you can't change log levels at runtime.

spring-shell-docs/modules/ROOT/pages/customization/singlecommand.adoc

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+[[using-shell-customization-singlecommand]]
+= Single Command
+:page-section-summary-toc: 1
+
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+If your shell application is made for exactly a single purpose having only one
+command it may be beneficial to configure it for this. Property
+`spring.shell.noninteractive.primary-command` if defined will disable all other
+runners than `NonInteractiveShellRunner` and configures it to use
+defined _Primary Command_.
+
+[source, yaml]
+----
+spring:
+  shell:
+    noninteractive:
+      primary-command: mycommand
+----
+
+For example if you have a command `mycommand` with option `arg`
+it had to be executed with `<shellapp> mycommand --arg hi`, but with above
+setting it can be executed with `<shellapp> --arg hi`.

spring-shell-docs/modules/ROOT/pages/customization/styling.adoc

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+[[theming]]
+= Theming
+
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Current terminal implementations are rich in features and can usually show
+something else that just plain text. For example a text can be styled to be
+_bold_ or have different colors. It's also common for terminals to be able
+to show various characters from an unicode table like emoji's which are usually
+used to make shell output more pretty.
+
+Spring Shell supports these via it's theming framework which contains two parts,
+firstly _styling_ can be used to change text type and secondly _figures_ how
+some characters are shown. These two are then combined together as a _theme_.
+
+More about _theming_ internals, see xref:appendices-techical-intro-theming.adoc[Theming].
+
+NOTE: Default theme is named `default` but can be change using property
+`spring.shell.theme.name`. Other built-in theme named `dump` uses
+no styling for colors and tries to not use any special figures.
+
+Modify existing style by overriding settings.
+
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=custom-style-class]
+----
+
+Modify existing figures by overriding settings.
+
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=custom-figure-class]
+----
+
+To create a new theme, create a `ThemeSettings` and provide your own _style_
+and _figure_ implementations.
+
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=custom-theme-class]
+----
+
+Register a new bean `Theme` where you can return your custom `ThemeSettings`
+and a _theme_ name.
+
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=custom-theme-config]
+----
+
+You can use `ThemeResolver` to resolve _styles_ if you want to create
+JLine-styled strings programmatically and _figures_ if you want to
+theme characters for being more pretty.
+
+[source, java, indent=0]
+----
+include::{snippets}/ThemingSnippets.java[tag=using-theme-resolver]
+----