Flatten docs structure

- Essentially remove "Using Spring Shell" and move
  its content one level up.
- Fixes #433

spring-shell-docs/src/main/asciidoc/introduction.adoc

@@ -9,6 +9,15 @@ The Spring Shell project provides the infrastructure to create such a REPL (Read
 Print Loop) application, letting you concentrate on implementing commands by using
 the familiar Spring programming model.
 
-Spring Shell includes advanced features (such as parsing, tab completion, colorization of 
+Spring Shell includes advanced features (such as parsing, tab completion, colorization of
 output, fancy ASCII-art table display, input conversion, and validation), freeing you
 to focus on core command logic.
+
+[IMPORTANT]
+====
+Spring Shell 2.1.x is a major rework to bring the codebase up to date with
+existing Spring Boot versions, adding new features and, especially,
+making it work with GraalVM which makes command-line applications much
+more relevant in a Java space. Moving to a new major version also lets
+us clean up the codebase and make some needed breaking changes.
+====

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

@@ -1,5 +1,5 @@
 [[using-shell-basics]]
-=== Basics
+== Basics
 This section covers the basics of Spring Shell. Before going on to define actual commands and options,
 we need to go through some of the fundamental concepts of Spring Shell.
 

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

@@ -1,10 +1,10 @@
 [[using-shell-building]]
-=== Building
+== Building
 
 This section covers how to build a Spring Shell application.
 
 [[native]]
-==== Native Support
+=== Native Support
 
 Version 2.1.x includes experimental support for compiling Spring Shell applications
 into native applications with GraalVM and Spring Native. Because the underlying JLine

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

@@ -1,4 +1,4 @@
-==== Annotation Model
+=== Annotation Model
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 When you use the standard API, methods on beans are turned into executable commands, provided that:

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

@@ -1,5 +1,5 @@
 [[dynamic-command-availability]]
-==== Dynamic Command Availability
+=== Dynamic Command Availability
 
 Registered commands do not always make sense, due to the internal state of the application.
 For example, there may be a `download` command, but it only works once the user has used `connect` on a remote

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

@@ -1,5 +1,5 @@
 [[dynamic-command-exitcode]]
-==== Exit Code
+=== Exit Code
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Many command line applications when applicable return an _exit code_ which running environment

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

@@ -1,5 +1,5 @@
 [[organizing-commands]]
-==== Organizing Commands
+=== Organizing Commands
 
 When your shell starts to provide a lot of functionality, you may end up
 with a lot of commands, which could be confusing for your users. By typing `help`,

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

@@ -1,4 +1,4 @@
-==== Programmatic Model
+=== Programmatic Model
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 In the programmatic model, `CommandRegistration` is defined as a `@Bean`, and it is automatically registered:

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

@@ -1,4 +1,4 @@
-=== Commands
+== Commands
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 In this section, we go through an actual command registration and leave command options

spring-shell-docs/src/main/asciidoc/using-shell-components-builtin.adoc

@@ -1,8 +1,8 @@
 [[built-in-commands]]
-==== Built-In Commands
+=== Built-In Commands
 
 [[help-command]]
-===== Help
+==== Help
 
 Running a shell application often implies that the user is in a graphically limited
 environment. Also, while we are nearly always connected in the era of mobile phones,
@@ -79,17 +79,17 @@ script: Read and execute commands from a file.
 ----
 ====
 
-===== Clear
+==== Clear
 The `clear` command does what you would expect and clears the screen, resetting the prompt
 in the top left corner.
 
-===== Exit
+==== Exit
 
 The `quit` command (also aliased as `exit`) requests the shell to quit, gracefully
 closing the Spring application context. If not overridden, a JLine `History` bean writes a history of all
 commands to disk, so that they are available again on the next launch.
 
-===== Stacktrace
+==== Stacktrace
 
 When an exception occurs inside command code, it is caught by the shell and a simple, one-line message is displayed
 so as not to overflow the user with too much information.
@@ -99,14 +99,14 @@ To this end, Spring Shell remembers the last exception that occurred, and the us
 command to print all the details on the console.
 
 [[script-command]]
-===== Script
+==== Script
 
 The `script` command accepts a local file as an argument and replays commands found there, one at a time.
 
 Reading from the file behaves exactly like inside the interactive shell, so lines starting with `//` are considered
 to be comments and are ignored, while lines ending with `\` trigger line continuation.
 
-===== History
+==== History
 
 The `history` command shows the history of commands that has been executed.
 
@@ -122,7 +122,7 @@ a placeholder (`{userconfig}`), which resolves to a common shared config directo
 
 TIP: Run the Spring Shell application to see how the sample application works as it uses these options.
 
-===== Completion
+==== Completion
 
 The `completion` command set lets you create script files that can be used
 with am OS shell implementations to provide completion. This is very useful when
@@ -130,7 +130,7 @@ working with non-interactive mode.
 
 Currently, the only implementation is for bash, which works with `bash` sub-command.
 
-===== Version
+==== Version
 
 The `version` command shows existing build and git info by integrating into
 Boot's `BuildProperties` and `GitProperties` if those exist in the shell application.

spring-shell-docs/src/main/asciidoc/using-shell-components-flow.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-flow]]
-==== Flow
+=== Flow
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 When you use <<using-shell-components-ui>> to build something that involves

spring-shell-docs/src/main/asciidoc/using-shell-components-ui-confirmation.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui-confirmation]]
-===== Confirmation
+==== Confirmation
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 The confirmation component asks a user for a simple confirmation. It is essentially a

spring-shell-docs/src/main/asciidoc/using-shell-components-ui-multiselect.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui-multiselect]]
-===== Multi Select
+==== Multi Select
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 The multi select component asks a user to select multiple items from a list.

spring-shell-docs/src/main/asciidoc/using-shell-components-ui-pathinput.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui-pathinput]]
-===== Path Input
+==== Path Input
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 The path input component asks a user for a `Path` and gives additional information about a path itself.

spring-shell-docs/src/main/asciidoc/using-shell-components-ui-render.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui-render]]
-===== Component Render
+==== Component Render
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 You can implement component rendering in either of two ways: fully

spring-shell-docs/src/main/asciidoc/using-shell-components-ui-singleselect.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui-singleselect]]
-===== Single Select
+==== Single Select
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 A single select component asks a user to choose one item from a list. It is similar to a simple

spring-shell-docs/src/main/asciidoc/using-shell-components-ui-stringinput.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui-stringinput]]
-===== String Input
+==== String Input
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 The string input component asks a user for simple text input, optionally masking values

spring-shell-docs/src/main/asciidoc/using-shell-components-ui.adoc

@@ -1,5 +1,5 @@
 [[using-shell-components-ui]]
-==== Flow Components
+=== Flow Components
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Starting from version 2.1.x, a new component model provides an

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

@@ -1,5 +1,5 @@
 [[using-shell-components]]
-=== Components
+== Components
 
 Components are a set of features which are either build-in or something
 you can re-use or extend for your own needs. Components in question are

spring-shell-docs/src/main/asciidoc/using-shell-customization-styling.adoc

@@ -1,5 +1,5 @@
 [[theming]]
-==== Theming
+=== Theming
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Current terminal implementations are rich in features and can usually show

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

@@ -1,5 +1,5 @@
 [[using-shell-customization]]
-=== Customization
+== Customization
 
 This section describes how you can customize the shell.
 

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

@@ -1,8 +1,8 @@
-=== Execution
+== Execution
 
 This section describes how to set up a Spring Shell to work in interactive mode.
 
-==== Interaction Mode
+=== Interaction Mode
 
 Version 2.1.x introduced built-in support to distinguish between interactive
 and non-interactive modes. This makes it easier to use the shell as a

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

@@ -1,5 +1,5 @@
 [[using-shell-options-arity]]
-==== Arity
+=== Arity
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Sometimes, you want to have more fine control of how many parameters with an option

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

@@ -1,5 +1,5 @@
 [[using-shell-options-default]]
-==== Default Value
+=== Default Value
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Having a default value for an option is somewhat related to

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

@@ -1,5 +1,5 @@
 [[using-shell-options-definition]]
-==== Definition
+=== Definition
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Options can be defined within a target method as annotations in a method arguments

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

@@ -1,5 +1,5 @@
 [[using-shell-options-label]]
-==== Label
+=== Label
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 _Option Label_ has no functional behaviour within a shell itself other than

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

@@ -1,5 +1,5 @@
 [[using-shell-options-optional]]
-==== Optional Value
+=== Optional Value
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 An option is either required or not and, generally speaking, how it behavesit depends on

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

@@ -1,5 +1,5 @@
 [[using-shell-options-positional]]
-==== Positional
+=== Positional
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Positional information is mostly related to a command target method:

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

@@ -1,5 +1,5 @@
 [[using-shell-options-short]]
-==== Short Format
+=== Short Format
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Short style _POSIX_ option in most is just a synonym to long format but

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

@@ -1,5 +1,5 @@
 [[validating-command-arguments]]
-==== Validation
+=== Validation
 
 Spring Shell integrates with the https://beanvalidation.org/[Bean Validation API] to support
 automatic and self-documenting constraints on command parameters.

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

@@ -1,5 +1,5 @@
 [[using-shell-options]]
-=== Options
+== Options
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Command line arguments can be separated into options and positional parameters.

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

@@ -1,15 +1,3 @@
-== Using Spring Shell
-This section describes how to use Spring Shell.
-
-[IMPORTANT]
-====
-Spring Shell 2.1.x is a major rework to bring the codebase up to date with
-existing Spring Boot versions, adding new features and, especially,
-making it work with GraalVM which makes command-line applications much
-more relevant in a Java space. Moving to a new major version also lets
-us clean up the codebase and make some needed breaking changes.
-====
-
 include::using-shell-basics.adoc[]
 
 include::using-shell-commands.adoc[]