Add podman farm list command

The podman farm list command allows users to list
the existing farms.

Signed-off-by: Urvashi Mohnani <umohnani@redhat.com>

cmd/podman/farm/list.go

@@ -0,0 +1,119 @@
+package farm
+
+import (
+	"fmt"
+	"os"
+	"sort"
+
+	"github.com/containers/common/pkg/completion"
+	"github.com/containers/common/pkg/config"
+	"github.com/containers/common/pkg/report"
+	"github.com/containers/podman/v4/cmd/podman/common"
+	"github.com/containers/podman/v4/cmd/podman/registry"
+	"github.com/containers/podman/v4/cmd/podman/validate"
+	"github.com/spf13/cobra"
+)
+
+var (
+	farmLsDescription = `podman farm ls
+
+List all available farms. The output of the farms can be filtered
+and the output format can be changed to JSON or a user specified Go template.`
+	lsCommand = &cobra.Command{
+		Use:               "list [options]",
+		Aliases:           []string{"ls"},
+		Args:              validate.NoArgs,
+		Short:             "List all existing farms",
+		Long:              farmLsDescription,
+		RunE:              list,
+		ValidArgsFunction: completion.AutocompleteNone,
+	}
+
+	// Temporary struct to hold cli values.
+	lsOpts = struct {
+		Format string
+	}{}
+)
+
+func init() {
+	registry.Commands = append(registry.Commands, registry.CliCommand{
+		Command: lsCommand,
+		Parent:  farmCmd,
+	})
+	flags := lsCommand.Flags()
+
+	formatFlagName := "format"
+	flags.StringVar(&lsOpts.Format, formatFlagName, "", "Format farm output using Go template")
+	_ = lsCommand.RegisterFlagCompletionFunc(formatFlagName, common.AutocompleteFormat(&farmOut{}))
+}
+
+type farmOut struct {
+	Name        string
+	Connections []string
+	Default     bool
+}
+
+func list(cmd *cobra.Command, args []string) error {
+	cfg, err := config.ReadCustomConfig()
+	if err != nil {
+		return err
+	}
+
+	format := lsOpts.Format
+	if format == "" && len(args) > 0 {
+		format = "json"
+	}
+
+	rows := make([]farmOut, 0)
+	for k, v := range cfg.Farms.List {
+		defaultFarm := false
+		if k == cfg.Farms.Default {
+			defaultFarm = true
+		}
+
+		r := farmOut{
+			Name:        k,
+			Connections: v,
+			Default:     defaultFarm,
+		}
+		rows = append(rows, r)
+	}
+
+	sort.Slice(rows, func(i, j int) bool {
+		return rows[i].Name < rows[j].Name
+	})
+
+	rpt := report.New(os.Stdout, cmd.Name())
+	defer rpt.Flush()
+
+	if report.IsJSON(format) {
+		buf, err := registry.JSONLibrary().MarshalIndent(rows, "", "    ")
+		if err == nil {
+			fmt.Println(string(buf))
+		}
+		return err
+	}
+
+	if format != "" {
+		rpt, err = rpt.Parse(report.OriginUser, format)
+	} else {
+		rpt, err = rpt.Parse(report.OriginPodman,
+			"{{range .}}{{.Name}}\t{{.Connections}}\t{{.Default}}\n{{end -}}")
+	}
+	if err != nil {
+		return err
+	}
+
+	if rpt.RenderHeaders {
+		err = rpt.Execute([]map[string]string{{
+			"Default":     "Default",
+			"Connections": "Connections",
+			"Name":        "Name",
+		}})
+		if err != nil {
+			return err
+		}
+	}
+
+	return rpt.Execute(rows)
+}

docs/source/markdown/podman-farm-list.1.md

@@ -0,0 +1,38 @@
+% podman-farm-list 1
+
+## NAME
+podman\-farm\-list - List the existing farms
+
+## SYNOPSIS
+**podman farm list** [*options*]
+
+**podman farm ls** [*options*]
+
+## DESCRIPTION
+List all the existing farms.
+
+## OPTIONS
+
+#### **--format**, **-f**=*format*
+
+Change the default output format.  This can be of a supported type like 'json' or a Go template.
+Valid placeholders for the Go template listed below:
+
+| **Placeholder** | **Description**                            |
+| --------------- | ------------------------------------------ |
+| .Connections    | List of all system connections in the farm |
+| .Default        | Indicates whether farm is the default      |
+| .Name           | Farm name                                  |
+
+## EXAMPLE
+```
+$ podman farm list
+Name        Connections  Default
+farm1       [f38 f37]    false
+farm2       [f37]        true
+```
+## SEE ALSO
+**[podman(1)](podman.1.md)**, **[podman-farm(1)](podman-farm.1.md)**
+
+## HISTORY
+July 2023, Originally compiled by Urvashi Mohnani (umohnani at redhat dot com)