Install shell completion as an optional command

registry.go

@@ -6,6 +6,7 @@ import (
 	"sort"
 
 	internalalias "gitea.maximumdirect.net/eric/CommandKit/internal/alias"
+	internalcobra "gitea.maximumdirect.net/eric/CommandKit/internal/cobra"
 	"gitea.maximumdirect.net/eric/CommandKit/internal/commandpath"
 )
 
@@ -122,6 +123,16 @@ func (a *App) buildInstallationCandidate(commands []Command, addedRules []Routin
 	if !sameRoutingRules(rules, a.routingRules) {
 		candidate.changed = true
 	}
+	if node := candidate.commands["completion"]; node != nil && node.command.record.completion {
+		if _, exists := candidate.commands[internalcobra.CompletionQueryToken]; exists {
+			return nil, fmt.Errorf("command path %q is reserved for completion", internalcobra.CompletionQueryToken)
+		}
+		for _, rule := range rules {
+			if rule.record.kind == commandAliasRule && len(rule.record.sourcePath) > 0 && rule.record.sourcePath[0] == internalcobra.CompletionQueryToken {
+				return nil, fmt.Errorf("command alias %q conflicts with completion", rule.record.sourcePath.String())
+			}
+		}
+	}
 
 	var mappings []internalalias.Mapping
 	for _, rule := range rules {