Split plugin commands into individual files

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

cmd/flux/plugin_install.go

@@ -0,0 +1,80 @@
+/*
+Copyright 2026 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/spf13/cobra"
+
+	"github.com/fluxcd/flux2/v2/internal/plugin"
+)
+
+var pluginInstallCmd = &cobra.Command{
+	Use:   "install <name>[@<version>]",
+	Short: "Install a plugin from the catalog",
+	Long: `The plugin install command downloads and installs a plugin from the Flux plugin catalog.
+
+Examples:
+  # Install the latest version
+  flux plugin install operator
+
+  # Install a specific version
+  flux plugin install operator@0.45.0`,
+	Args: cobra.ExactArgs(1),
+	RunE: pluginInstallCmdRun,
+}
+
+func init() {
+	pluginCmd.AddCommand(pluginInstallCmd)
+}
+
+func pluginInstallCmdRun(cmd *cobra.Command, args []string) error {
+	nameVersion := args[0]
+	name, version := parseNameVersion(nameVersion)
+
+	catalogClient := newCatalogClient()
+	manifest, err := catalogClient.FetchManifest(name)
+	if err != nil {
+		return err
+	}
+
+	pv, err := plugin.ResolveVersion(manifest, version)
+	if err != nil {
+		return err
+	}
+
+	plat, err := plugin.ResolvePlatform(pv, runtime.GOOS, runtime.GOARCH)
+	if err != nil {
+		return fmt.Errorf("plugin %q v%s has no binary for %s/%s", name, pv.Version, runtime.GOOS, runtime.GOARCH)
+	}
+
+	pluginDir := pluginHandler.EnsurePluginDir()
+
+	installer := plugin.NewInstaller()
+	sp := newPluginSpinner(fmt.Sprintf("installing %s v%s", name, pv.Version))
+	sp.Start()
+	if err := installer.Install(pluginDir, manifest, pv, plat); err != nil {
+		sp.Stop()
+		return err
+	}
+	sp.Stop()
+
+	logger.Successf("installed %s v%s", name, pv.Version)
+	return nil
+}