feat: add --dry-run flag to action commands

Adds a persistent --dry-run flag that shows matched tasks without
performing mutations. Supported on done, delete, modify, start, and stop
commands. Also fixes preprocessArgs to skip flag-like args when
identifying commands, preventing flags from being treated as filters.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

opal-task/cmd/delete.go

@@ -53,6 +53,12 @@ func deleteTasks(args []string) error {
 		return fmt.Errorf("no tasks matched filter")
 	}
 
+	if dryRunFlag {
+		fmt.Print(engine.FormatTaskConfirmList("delete", tasks, ws))
+		fmt.Println("Dry run — no changes made.")
+		return nil
+	}
+
 	if len(tasks) > 1 {
 		fmt.Print(engine.FormatTaskConfirmList("delete", tasks, ws))
 		fmt.Printf("Proceed? (y/N): ")

opal-task/cmd/done.go

@@ -66,6 +66,12 @@ func completeTasks(args []string) error {
 		return fmt.Errorf("no tasks matched filter")
 	}
 
+	if dryRunFlag {
+		fmt.Print(engine.FormatTaskConfirmList("complete", tasks, ws))
+		fmt.Println("Dry run — no changes made.")
+		return nil
+	}
+
 	if len(tasks) > 1 {
 		fmt.Print(engine.FormatTaskConfirmList("complete", tasks, ws))
 		fmt.Printf("Proceed? (y/N): ")

opal-task/cmd/modify.go

@@ -85,6 +85,12 @@ func modifyTasks(filterArgs, modifierArgs []string) error {
 		return fmt.Errorf("no tasks matched filter")
 	}
 
+	if dryRunFlag {
+		fmt.Print(engine.FormatTaskConfirmList("modify", tasks, ws))
+		fmt.Println("Dry run — no changes made.")
+		return nil
+	}
+
 	// Confirm if multiple tasks or no filters specified
 	if len(tasks) > 1 || len(filterArgs) == 0 {
 		fmt.Print(engine.FormatTaskConfirmList("modify", tasks, ws))

opal-task/cmd/root.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"strings"
 
 	"git.jnss.me/joakim/opal/internal/engine"
 	"github.com/spf13/cobra"
@@ -25,6 +26,7 @@ const parsedArgsKey contextKey = "parsedArgs"
 var (
 	configDirFlag string
 	dataDirFlag   string
+	dryRunFlag    bool
 )
 
 // Command classification
@@ -120,6 +122,7 @@ func getParsedArgs(cmd *cobra.Command) *ParsedArgs {
 
 // preprocessArgs parses command-line arguments before Cobra routing
 // Returns: command name, filters, modifiers
+// Flags (--foo) are stripped from filters/modifiers; Cobra handles them from os.Args.
 func preprocessArgs(args []string) *ParsedArgs {
 	if len(args) == 0 {
 		return &ParsedArgs{
@@ -129,11 +132,14 @@ func preprocessArgs(args []string) *ParsedArgs {
 		}
 	}
 
-	// Find command position (check both regular commands and reports)
+	// Find command position, skipping flag-like args
 	cmdIdx := -1
 	cmdName := ""
 
 	for i, arg := range args {
+		if strings.HasPrefix(arg, "-") {
+			continue // Skip flags — Cobra handles them
+		}
 		// Check regular commands
 		for _, name := range commandNames {
 			if arg == name {
@@ -161,30 +167,26 @@ func preprocessArgs(args []string) *ParsedArgs {
 	if cmdIdx == -1 {
 		return &ParsedArgs{
 			Command:   "list",
-			Filters:   args,
+			Filters:   stripFlags(args),
 			Modifiers: []string{},
 		}
 	}
 
 	// Split arguments around command
-	leftArgs := args[:cmdIdx] // Everything before command
+	leftArgs := stripFlags(args[:cmdIdx])
 	rightArgs := []string{}
 	if cmdIdx+1 < len(args) {
-		rightArgs = args[cmdIdx+1:] // Everything after command
+		rightArgs = stripFlags(args[cmdIdx+1:])
 	}
 
 	// Determine how to interpret right args
 	if commandsWithModifiers[cmdName] {
-		// Command accepts modifiers
-		// Left = filters, Right = modifiers
 		return &ParsedArgs{
 			Command:   cmdName,
 			Filters:   leftArgs,
 			Modifiers: rightArgs,
 		}
 	} else {
-		// Command doesn't accept modifiers
-		// Both left and right are filters
 		allFilters := append(leftArgs, rightArgs...)
 		return &ParsedArgs{
 			Command:   cmdName,
@@ -194,12 +196,25 @@ func preprocessArgs(args []string) *ParsedArgs {
 	}
 }
 
+// stripFlags removes flag-like args (starting with -) from a slice
+func stripFlags(args []string) []string {
+	var result []string
+	for _, arg := range args {
+		if !strings.HasPrefix(arg, "-") {
+			result = append(result, arg)
+		}
+	}
+	return result
+}
+
 func init() {
 	// Add persistent flags for directory overrides
 	rootCmd.PersistentFlags().StringVar(&configDirFlag, "config-dir", "",
 		"Config directory (default: $XDG_CONFIG_HOME/opal or ~/.config/opal)")
 	rootCmd.PersistentFlags().StringVar(&dataDirFlag, "data-dir", "",
 		"Data directory (default: $XDG_DATA_HOME/opal or ~/.local/share/opal)")
+	rootCmd.PersistentFlags().BoolVar(&dryRunFlag, "dry-run", false,
+		"Show matched tasks without performing the action")
 
 	// Use PersistentPreRun for initialization (runs for all subcommands unless overridden)
 	rootCmd.PersistentPreRun = func(cmd *cobra.Command, args []string) {

opal-task/cmd/start.go

@@ -47,6 +47,12 @@ func startTasks(args []string) error {
 		return fmt.Errorf("no tasks matched filter")
 	}
 
+	if dryRunFlag {
+		fmt.Print(engine.FormatTaskConfirmList("start", tasks, ws))
+		fmt.Println("Dry run — no changes made.")
+		return nil
+	}
+
 	for _, task := range tasks {
 		task.StartTask()
 		fmt.Printf("Started task: %s\n", task.Description)

opal-task/cmd/stop.go

@@ -47,6 +47,12 @@ func stopTasks(args []string) error {
 		return fmt.Errorf("no tasks matched filter")
 	}
 
+	if dryRunFlag {
+		fmt.Print(engine.FormatTaskConfirmList("stop", tasks, ws))
+		fmt.Println("Dry run — no changes made.")
+		return nil
+	}
+
 	for _, task := range tasks {
 		task.StopTask()
 		fmt.Printf("Stopped task: %s\n", task.Description)