perf: Optimize memory allocations and string operations

internal/envfiles/parse.go

@@ -99,7 +99,7 @@ func ParseEnvFile(path string) (map[string]string, error) {
 // Each line in the file is a path to add.
 // If the file doesn't exist, an empty slice is returned without error.
 func ParsePathFile(path string) ([]string, error) {
-	var result []string
+	result := make([]string, 0, 8) // Pre-allocate with reasonable initial capacity
 
 	file, err := os.Open(path)
 	if err != nil {

internal/envfiles/parse_test.go

@@ -197,7 +197,7 @@ func TestParsePathFile(t *testing.T) {
 		{
 			name:     "empty file",
 			content:  "",
-			expected: nil,
+			expected: []string{},
 		},
 		{
 			name:     "single path",

internal/workflow/load.go

@@ -64,7 +64,8 @@ func extractJobOrderFromNode(root *yaml.Node) []string {
 
 		if keyNode.Value == "jobs" && valueNode.Kind == yaml.MappingNode {
 			// Extract job IDs in order
-			var jobOrder []string
+			numJobs := len(valueNode.Content) / 2
+			jobOrder := make([]string, 0, numJobs)
 			for j := 0; j < len(valueNode.Content)-1; j += 2 {
 				jobKeyNode := valueNode.Content[j]
 				jobOrder = append(jobOrder, jobKeyNode.Value)

internal/workflow/load_test.go

@@ -299,28 +299,30 @@ jobs:
 // BenchmarkLoadWorkflowFile benchmarks the workflow file loading performance.
 func BenchmarkLoadWorkflowFile(b *testing.B) {
 	// Create a workflow with multiple jobs and steps to simulate realistic usage
-	yamlContent := `name: Benchmark Workflow
+	var builder strings.Builder
+	builder.WriteString(`name: Benchmark Workflow
 env:
   GLOBAL_VAR: global_value
 jobs:
-`
+`)
 	// Add multiple jobs with multiple steps
 	for i := 0; i < 10; i++ {
-		yamlContent += fmt.Sprintf(`  job%d:
+		fmt.Fprintf(&builder, `  job%d:
     name: Job %d
     runs-on: ubuntu-latest
     env:
       JOB_VAR: job_value_%d
     steps:
 `, i, i, i)
 		for j := 0; j < 5; j++ {
-			yamlContent += fmt.Sprintf(`      - name: Step %d-%d
+			fmt.Fprintf(&builder, `      - name: Step %d-%d
         run: echo "Running step %d in job %d"
         env:
           STEP_VAR: step_value_%d_%d
 `, i, j, j, i, i, j)
 		}
 	}
+	yamlContent := builder.String()
 
 	tmpDir := b.TempDir()
 	workflowPath := filepath.Join(tmpDir, "benchmark.yml")

internal/workflow/select.go

@@ -47,15 +47,15 @@ func DiscoverWorkflows(repoRoot string) ([]string, error) {
 		return nil, fmt.Errorf("failed to read workflows directory: %w", err)
 	}
 
-	var workflows []string
+	workflows := make([]string, 0, len(entries))
 	for _, entry := range entries {
 		if entry.IsDir() {
 			continue
 		}
 
 		name := entry.Name()
-		ext := strings.ToLower(filepath.Ext(name))
-		if ext == ".yml" || ext == ".yaml" {
+		ext := filepath.Ext(name)
+		if strings.EqualFold(ext, ".yml") || strings.EqualFold(ext, ".yaml") {
 			workflows = append(workflows, filepath.Join(workflowsDir, name))
 		}
 	}