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>

2 files changed, 46 insertions, 17 deletions

diff --git a/cmd/podman/generate/kube.go b/cmd/podman/generate/kube.go
index 87f7501e3..e47bd35b5 100644
--- a/cmd/podman/generate/kube.go
+++ b/cmd/podman/generate/kube.go
@@ -5,6 +5,8 @@ import (
 	"io/ioutil"
 	"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/cmd/podman/utils"
 	"github.com/containers/podman/v2/pkg/domain/entities"
@@ -20,11 +22,12 @@ var (
 Whether the input is for a container or pod, Podman will always generate the specification as a pod.`
 
 	kubeCmd = &cobra.Command{
-		Use:   "kube [options] CONTAINER | POD",
-		Short: "Generate Kubernetes YAML from a container or pod.",
-		Long:  kubeDescription,
-		RunE:  kube,
-		Args:  cobra.ExactArgs(1),
+		Use:               "kube [options] CONTAINER | POD",
+		Short:             "Generate Kubernetes YAML from a container or pod.",
+		Long:              kubeDescription,
+		RunE:              kube,
+		Args:              cobra.ExactArgs(1),
+		ValidArgsFunction: common.AutocompleteContainersAndPods,
 		Example: `podman generate kube ctrID
   podman generate kube podID
   podman generate kube --service podID`,
@@ -39,7 +42,11 @@ func init() {
 	})
 	flags := kubeCmd.Flags()
 	flags.BoolVarP(&kubeOptions.Service, "service", "s", false, "Generate YAML for a Kubernetes service object")
-	flags.StringVarP(&kubeFile, "filename", "f", "", "Write output to the specified path")
+
+	filenameFlagName := "filename"
+	flags.StringVarP(&kubeFile, filenameFlagName, "f", "", "Write output to the specified path")
+	_ = kubeCmd.RegisterFlagCompletionFunc(filenameFlagName, completion.AutocompleteDefault)
+
 	flags.SetNormalizeFunc(utils.AliasFlags)
 }
 
diff --git a/cmd/podman/generate/systemd.go b/cmd/podman/generate/systemd.go
index 8e937fa90..e9cf76aae 100644
--- a/cmd/podman/generate/systemd.go
+++ b/cmd/podman/generate/systemd.go
@@ -6,7 +6,9 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/containers/common/pkg/completion"
 	"github.com/containers/common/pkg/report"
+	"github.com/containers/podman/v2/cmd/podman/common"
 	"github.com/containers/podman/v2/cmd/podman/registry"
 	"github.com/containers/podman/v2/cmd/podman/utils"
 	"github.com/containers/podman/v2/pkg/domain/entities"
@@ -24,11 +26,12 @@ var (
   The generated units can later be controlled via systemctl(1).`
 
 	systemdCmd = &cobra.Command{
-		Use:   "systemd [options] CTR|POD",
-		Short: "Generate systemd units.",
-		Long:  systemdDescription,
-		RunE:  systemd,
-		Args:  cobra.ExactArgs(1),
+		Use:               "systemd [options] CTR|POD",
+		Short:             "Generate systemd units.",
+		Long:              systemdDescription,
+		RunE:              systemd,
+		Args:              cobra.ExactArgs(1),
+		ValidArgsFunction: common.AutocompleteContainersAndPods,
 		Example: `podman generate systemd CTR
   podman generate systemd --new --time 10 CTR
   podman generate systemd --files --name POD`,
@@ -44,13 +47,32 @@ func init() {
 	flags := systemdCmd.Flags()
 	flags.BoolVarP(&systemdOptions.Name, "name", "n", false, "Use container/pod names instead of IDs")
 	flags.BoolVarP(&files, "files", "f", false, "Generate .service files instead of printing to stdout")
-	flags.UintVarP(&systemdTimeout, "time", "t", containerConfig.Engine.StopTimeout, "Stop timeout override")
-	flags.StringVar(&systemdOptions.RestartPolicy, "restart-policy", "on-failure", "Systemd restart-policy")
+
+	timeFlagName := "time"
+	flags.UintVarP(&systemdTimeout, timeFlagName, "t", containerConfig.Engine.StopTimeout, "Stop timeout override")
+	_ = systemdCmd.RegisterFlagCompletionFunc(timeFlagName, completion.AutocompleteNone)
 	flags.BoolVarP(&systemdOptions.New, "new", "", false, "Create a new container instead of starting an existing one")
-	flags.StringVar(&systemdOptions.ContainerPrefix, "container-prefix", "container", "Systemd unit name prefix for containers")
-	flags.StringVar(&systemdOptions.PodPrefix, "pod-prefix", "pod", "Systemd unit name prefix for pods")
-	flags.StringVar(&systemdOptions.Separator, "separator", "-", "Systemd unit name separator between name/id and prefix")
-	flags.StringVar(&format, "format", "", "Print the created units in specified format (json)")
+
+	containerPrefixFlagName := "container-prefix"
+	flags.StringVar(&systemdOptions.ContainerPrefix, containerPrefixFlagName, "container", "Systemd unit name prefix for containers")
+	_ = systemdCmd.RegisterFlagCompletionFunc(containerPrefixFlagName, completion.AutocompleteNone)
+
+	podPrefixFlagName := "pod-prefix"
+	flags.StringVar(&systemdOptions.PodPrefix, podPrefixFlagName, "pod", "Systemd unit name prefix for pods")
+	_ = systemdCmd.RegisterFlagCompletionFunc(podPrefixFlagName, completion.AutocompleteNone)
+
+	separatorFlagName := "separator"
+	flags.StringVar(&systemdOptions.Separator, separatorFlagName, "-", "Systemd unit name separator between name/id and prefix")
+	_ = systemdCmd.RegisterFlagCompletionFunc(separatorFlagName, completion.AutocompleteNone)
+
+	restartPolicyFlagName := "restart-policy"
+	flags.StringVar(&systemdOptions.RestartPolicy, restartPolicyFlagName, "on-failure", "Systemd restart-policy")
+	_ = systemdCmd.RegisterFlagCompletionFunc(restartPolicyFlagName, common.AutocompleteSystemdRestartOptions)
+
+	formatFlagName := "format"
+	flags.StringVar(&format, formatFlagName, "", "Print the created units in specified format (json)")
+	_ = systemdCmd.RegisterFlagCompletionFunc(formatFlagName, common.AutocompleteJSONFormat)
+
 	flags.SetNormalizeFunc(utils.AliasFlags)
 }