Add a dry run flag

instruction_test.go

@@ -394,6 +394,35 @@ func TestLinkInstruction_RunAsync(t *testing.T) {
 		assert.Contains(t, err.Error(), "files=true")
 		assert.True(t, FileExists(targetDir))
 	})
+
+	t.Run("Dry run does not modify filesystem", func(t *testing.T) {
+		originalFS := filesystem
+		filesystem = NewDryRunFileSystem()
+		defer func() {
+			filesystem = originalFS
+		}()
+
+		target := filepath.Join(testDir, "dryrun-link.txt")
+		instruction := LinkInstruction{
+			Source: srcFile,
+			Target: target,
+			Force:  true,
+			Delete: true,
+		}
+
+		status := make(chan error)
+		go instruction.RunAsync(status)
+
+		err := <-status
+		assert.NoError(t, err)
+		assert.False(t, FileExists(target))
+
+		summary := filesystem.SummaryLines()
+		assert.Equal(t, 1, len(summary))
+		assert.Contains(t, summary[0], "DRY-RUN")
+		assert.Contains(t, summary[0], srcFile)
+		assert.Contains(t, summary[0], target)
+	})
 }
 
 func TestLinkInstruction_Undo(t *testing.T) {