feat(cli): add manifest delete command

Implement manifest delete subcommand to allow users to remove flags
from their manifest file via the CLI. This complements the existing
add subcommand and provides complete flag lifecycle management.

Features:
- Command validates flag exists before deletion
- Uses atomic temp file pattern for safe I/O operations
- Provides clear success/error feedback
- Follows existing CLI patterns and conventions
- Includes comprehensive unit tests (9 test cases)
- Handles edge cases (empty manifest, non-existent flags, etc.)

Fixes #154

Author: reckziegelwilliam

internal/cmd/manifest.go

@@ -21,6 +21,7 @@ func GetManifestCmd() *cobra.Command {
 	// Add subcommands
 	manifestCmd.AddCommand(GetManifestAddCmd())
 	manifestCmd.AddCommand(GetManifestListCmd())
+	manifestCmd.AddCommand(GetManifestDeleteCmd())
 
 	addStabilityInfo(manifestCmd)
 

internal/cmd/manifest_delete.go

@@ -0,0 +1,90 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/open-feature/cli/internal/config"
+	"github.com/open-feature/cli/internal/filesystem"
+	"github.com/open-feature/cli/internal/logger"
+	"github.com/open-feature/cli/internal/manifest"
+	"github.com/pterm/pterm"
+	"github.com/spf13/afero"
+	"github.com/spf13/cobra"
+)
+
+func GetManifestDeleteCmd() *cobra.Command {
+	manifestDeleteCmd := &cobra.Command{
+		Use:   "delete <flag-name>",
+		Short: "Delete a flag from the manifest",
+		Long: `Delete a flag from the manifest file by its key.
+
+Examples:
+  # Delete a flag named 'old-feature'
+  openfeature manifest delete old-feature
+
+  # Delete a flag from a specific manifest file
+  openfeature manifest delete old-feature --manifest path/to/flags.json`,
+		Args: cobra.ExactArgs(1),
+		PreRunE: func(cmd *cobra.Command, args []string) error {
+			return initializeConfig(cmd, "manifest.delete")
+		},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			flagName := args[0]
+			manifestPath := config.GetManifestPath(cmd)
+
+			// Check if manifest exists
+			exists, err := afero.Exists(filesystem.FileSystem(), manifestPath)
+			if err != nil {
+				return fmt.Errorf("failed to check manifest existence: %w", err)
+			}
+
+			if !exists {
+				return fmt.Errorf("manifest file does not exist: %s", manifestPath)
+			}
+
+			// Load existing manifest
+			fs, err := manifest.LoadFlagSet(manifestPath)
+			if err != nil {
+				return fmt.Errorf("failed to load manifest: %w", err)
+			}
+
+			// Check if manifest has any flags
+			if len(fs.Flags) == 0 {
+				return fmt.Errorf("manifest contains no flags")
+			}
+
+			// Check if flag exists
+			flagIndex := -1
+			for i, flag := range fs.Flags {
+				if flag.Key == flagName {
+					flagIndex = i
+					break
+				}
+			}
+
+			if flagIndex == -1 {
+				return fmt.Errorf("flag '%s' not found in manifest", flagName)
+			}
+
+			// Remove the flag by creating a new slice without it
+			fs.Flags = append(fs.Flags[:flagIndex], fs.Flags[flagIndex+1:]...)
+
+			// Write updated manifest
+			if err := manifest.Write(manifestPath, *fs); err != nil {
+				return fmt.Errorf("failed to write manifest: %w", err)
+			}
+
+			// Success message
+			pterm.Success.Printfln("Flag '%s' deleted successfully from %s", flagName, manifestPath)
+			logger.Default.Debug(fmt.Sprintf("Deleted flag: name=%s, manifestPath=%s", flagName, manifestPath))
+
+			return nil
+		},
+	}
+
+	// Add command-specific flags
+	config.AddManifestDeleteFlags(manifestDeleteCmd)
+	addStabilityInfo(manifestDeleteCmd)
+
+	return manifestDeleteCmd
+}