feat: add --format json support to plugin:list

Adds a `--format json` flag to `plugin:list` whose output includes each plugin's install source - for git-based third-party plugins, the git remote URL, the checked-out commit, and the followed branch - so the set of installed plugins can be reconstructed elsewhere.

Closes #8798.

plugins/plugin/plugin_test.go

@@ -0,0 +1,45 @@
+package plugin
+
+import (
+	"testing"
+)
+
+func TestParsePlugnList(t *testing.T) {
+	output := `plugn: dev
+  00_dokku-standard    0.38.21 enabled    dokku core standard plugin
+  smoke-test-plugin    0.2.0 disabled   a third party plugin
+  bare-plugin          1.0.0 enabled`
+
+	plugins := parsePlugnList(output)
+	if len(plugins) != 3 {
+		t.Fatalf("expected 3 plugins, got %d", len(plugins))
+	}
+
+	first := plugins[0]
+	if first.Name != "00_dokku-standard" {
+		t.Errorf("expected name 00_dokku-standard, got %q", first.Name)
+	}
+	if first.Version != "0.38.21" {
+		t.Errorf("expected version 0.38.21, got %q", first.Version)
+	}
+	if !first.Enabled {
+		t.Errorf("expected plugin to be enabled")
+	}
+	if first.Description != "dokku core standard plugin" {
+		t.Errorf("expected multi-word description, got %q", first.Description)
+	}
+
+	if plugins[1].Enabled {
+		t.Errorf("expected smoke-test-plugin to be disabled")
+	}
+	if plugins[1].Description != "a third party plugin" {
+		t.Errorf("expected multi-word description, got %q", plugins[1].Description)
+	}
+
+	if plugins[2].Name != "bare-plugin" {
+		t.Errorf("expected name bare-plugin, got %q", plugins[2].Name)
+	}
+	if plugins[2].Description != "" {
+		t.Errorf("expected empty description, got %q", plugins[2].Description)
+	}
+}