Add shell completion with cobra

Allow automatic generation for shell completion scripts
with the internal cobra functions (requires v1.0.0+).

This should replace the handwritten completion scripts
and even adds support for fish. With this approach it is
less likley that completions and code are out of sync.

We can now create the scripts with
- podman completion bash
- podman completion zsh
- podman completion fish

To test the completion run:
source <(podman completion bash)

The same works for podman-remote and podman --remote and
it will complete your remote containers/images with
the correct endpoints values from --url/--connection.

The completion logic is written in go and provided by the
cobra library. The completion functions lives in
`cmd/podman/completion/completion.go`.

The unit test at cmd/podman/shell_completion_test.go checks
if each command and flag has an autocompletion function set.
This prevents that commands and flags have no shell completion set.

This commit does not replace the current autocompletion scripts.

Closes #6440

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

docs/source/markdown/podman-completion.1.md

@@ -0,0 +1,56 @@
+% podman-completion(1)
+
+## NAME
+podman\-completion - Generate shell completion scripts
+
+## SYNOPSIS
+**podman completion** [*options*] *bash*|*zsh*|*fish*
+
+## DESCRIPTION
+The completion command allows you to generate shell completion scripts. Supported shells are **bash**, **zsh** and **fish**.
+
+These script are used by the shell to provide suggestions and complete commands when you are typing the command and press [TAB].
+
+Usually these scripts are automatically installed via rpm/deb packages.
+
+## OPTIONS
+**--file**, **-f**
+
+Write the generated output to file.
+
+**--no-desc**
+
+Do not provide description in the completions.
+
+## Installation
+
+### BASH
+Make sure you have `bash-completion` installed on your system.
+
+To load the completion script into your current session run:
+`source <(podman completion bash)`
+
+To make it available in all your bash sessions run:
+`podman completion bash -f /etc/bash_completion.d/podman`
+
+
+### ZSH
+If shell completion is not already enabled in your environment you will need to enable it. You can execute the following once:
+`echo "autoload -U compinit; compinit" >> ~/.zshrc`
+
+To make it available in all your zsh sessions run:
+`podman completion zsh -f "${fpath[1]}/_podman"`
+
+Once you reload the shell the autocompletion should be working.
+
+
+### FISH
+To load the completion script into your current session run:
+`podman completion fish | source`
+
+To make it available in all your fish sessions run:
+`podman completion fish -f ~/.config/fish/completions/podman.fish`
+
+
+## SEE ALSO
+[podman(1)](podman.1.md)

docs/source/markdown/podman.1.md

@@ -205,6 +205,7 @@ the exit codes follow the `chroot` standard, see below:
 | [podman-auto-update(1)](podman-auto-update.1.md) | Auto update containers according to their auto-update policy                |
 | [podman-build(1)](podman-build.1.md)             | Build a container image using a Containerfile.                              |
 | [podman-commit(1)](podman-commit.1.md)           | Create new image based on the changed container.                            |
+| [podman-completion(1)](podman-completion.1.md)   | Generate shell completion scripts                                           |
 | [podman-container(1)](podman-container.1.md)     | Manage containers.                                                          |
 | [podman-cp(1)](podman-cp.1.md)                   | Copy files/folders between a container and the local filesystem.            |
 | [podman-create(1)](podman-create.1.md)           | Create a new container.                                                     |