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>

1 files changed, 19 insertions, 8 deletions

diff --git a/cmd/podman/images/sign.go b/cmd/podman/images/sign.go
index f6c1f9856..529fb3d92 100644
--- a/cmd/podman/images/sign.go
+++ b/cmd/podman/images/sign.go
@@ -3,6 +3,8 @@ package images
 import (
 	"os"
 
+	"github.com/containers/common/pkg/completion"
+	"github.com/containers/podman/v2/cmd/podman/common"
 	"github.com/containers/podman/v2/cmd/podman/registry"
 	"github.com/containers/podman/v2/pkg/domain/entities"
 	"github.com/pkg/errors"
@@ -12,11 +14,12 @@ import (
 var (
 	signDescription = "Create a signature file that can be used later to verify the image."
 	signCommand     = &cobra.Command{
-		Use:   "sign [options] IMAGE [IMAGE...]",
-		Short: "Sign an image",
-		Long:  signDescription,
-		RunE:  sign,
-		Args:  cobra.MinimumNArgs(1),
+		Use:               "sign [options] IMAGE [IMAGE...]",
+		Short:             "Sign an image",
+		Long:              signDescription,
+		RunE:              sign,
+		Args:              cobra.MinimumNArgs(1),
+		ValidArgsFunction: common.AutocompleteImages,
 		Example: `podman image sign --sign-by mykey imageID
   podman image sign --sign-by mykey --directory ./mykeydir imageID`,
 	}
@@ -33,9 +36,17 @@ func init() {
 		Parent:  imageCmd,
 	})
 	flags := signCommand.Flags()
-	flags.StringVarP(&signOptions.Directory, "directory", "d", "", "Define an alternate directory to store signatures")
-	flags.StringVar(&signOptions.SignBy, "sign-by", "", "Name of the signing key")
-	flags.StringVar(&signOptions.CertDir, "cert-dir", "", "`Pathname` of a directory containing TLS certificates and keys")
+	directoryFlagName := "directory"
+	flags.StringVarP(&signOptions.Directory, directoryFlagName, "d", "", "Define an alternate directory to store signatures")
+	_ = signCommand.RegisterFlagCompletionFunc(directoryFlagName, completion.AutocompleteDefault)
+
+	signByFlagName := "sign-by"
+	flags.StringVar(&signOptions.SignBy, signByFlagName, "", "Name of the signing key")
+	_ = signCommand.RegisterFlagCompletionFunc(signByFlagName, completion.AutocompleteNone)
+
+	certDirFlagName := "cert-dir"
+	flags.StringVar(&signOptions.CertDir, certDirFlagName, "", "`Pathname` of a directory containing TLS certificates and keys")
+	_ = signCommand.RegisterFlagCompletionFunc(certDirFlagName, completion.AutocompleteDefault)
 }
 
 func sign(cmd *cobra.Command, args []string) error {