add merge command

cmd/merge.go

@@ -0,0 +1,55 @@
+package cmd
+
+import (
+	"github.com/qiniu/goc/v2/pkg/log"
+	"github.com/spf13/cobra"
+	"golang.org/x/tools/cover"
+	"k8s.io/test-infra/gopherage/pkg/cov"
+	"k8s.io/test-infra/gopherage/pkg/util"
+)
+
+var mergeCmd = &cobra.Command{
+	Use:   "merge [files...]",
+	Short: "Merge multiple coherent Go coverage files into a single file.",
+	Long: `merge will merge multiple Go coverage files into a single coverage file.
+merge requires that the files are 'coherent', meaning that if they both contain references to the
+same paths, then the contents of those source files were identical for the binary that generated
+each file.
+`,
+	Run: func(cmd *cobra.Command, args []string) {
+		runMerge(args, outputMergeProfile)
+	},
+}
+
+var outputMergeProfile string
+
+func init() {
+	mergeCmd.Flags().StringVarP(&outputMergeProfile, "output", "o", "mergeprofile.cov", "output file")
+
+	rootCmd.AddCommand(mergeCmd)
+}
+
+func runMerge(args []string, output string) {
+	if len(args) == 0 {
+		log.Fatalf("Expected at least one coverage file.")
+	}
+
+	profiles := make([][]*cover.Profile, len(args))
+	for _, path := range args {
+		profile, err := util.LoadProfile(path)
+		if err != nil {
+			log.Fatalf("failed to open %s: %v", path, err)
+		}
+		profiles = append(profiles, profile)
+	}
+
+	merged, err := cov.MergeMultipleProfiles(profiles)
+	if err != nil {
+		log.Fatalf("failed to merge files: %v", err)
+	}
+
+	err = util.DumpProfile(output, merged)
+	if err != nil {
+		log.Fatalf("fail to dump the merged file: %v", err)
+	}
+}