accept -g to merge files

cmd/main.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"io"
 	"io/ioutil"
+	"log"
 	"os"
 
 	"gitea.inhome.blapointe.com/gogs/pttodo/pttodo"
@@ -26,16 +27,93 @@ func main() {
 
 func _main() error {
 	config := getConfig()
-	if err := add(&config); err != nil {
-		return err
+
+	if config.target2 != "" {
+		return merge(&config)
+	} else {
+		if err := add(&config); err != nil {
+			return err
+		}
+		if err := edit(&config); err != nil {
+			return err
+		}
+		return dump(config)
 	}
-	if err := edit(&config); err != nil {
-		return err
-	}
-	return dump(config)
 }
 
-func merge(filepath string, mergeTargetFilePath string) error {
+func merge(config *config) error {
+	if config.target2 == "" {
+		return nil
+	}
+
+	baseReader, err := filePathReader(config.target)
+	if err != nil {
+		return err
+	}
+	baseB, err := ioutil.ReadAll(baseReader)
+	if err != nil {
+		return err
+	}
+
+	mergingReader, err := filePathReader(config.target2)
+	if err != nil {
+		return err
+	}
+	mergingB, err := ioutil.ReadAll(mergingReader)
+	if err != nil {
+		return err
+	}
+
+	var base, merging pttodo.Root
+	if err := yaml.Unmarshal(baseB, &base); err != nil {
+		return err
+	}
+	if err := yaml.Unmarshal(mergingB, &merging); err != nil {
+		return err
+	}
+
+	slurp := func(dst, src *[]pttodo.Todo) {
+		_src := *src
+		for i := range _src {
+			found := false
+			for j := range *dst {
+				found = found || _src[i].Equals((*dst)[j])
+			}
+			if !found {
+				*dst = append(*dst, _src[i])
+			}
+		}
+	}
+	slurp(&base.Todo, &merging.Todo)
+	slurp(&base.Scheduled, &merging.Scheduled)
+	slurp(&base.Done, &merging.Done)
+
+	if tmppath, err := marshalRootToTempFile(base); err != nil {
+		return err
+	} else if config.dryRun {
+		log.Println("===before===")
+		_dump(os.Stdout, []string{config.target}, config.tags, config.search, config.root)
+		log.Println("===after===")
+		_dump(os.Stdout, []string{tmppath}, config.tags, config.search, config.root)
+	} else if err := rename(tmppath, config.target); err != nil {
+		return err
+	}
+
+	merging.Done = append(merging.Done, merging.Todo...)
+	merging.Todo = merging.Todo[:0]
+	merging.Scheduled = append(merging.Done, merging.Scheduled...)
+	merging.Scheduled = merging.Scheduled[:0]
+	if tmppath2, err := marshalRootToTempFile(merging); err != nil {
+		return err
+	} else if config.dryRun {
+	} else if err := rename(tmppath2, config.target2); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func _merge(filepath string, mergeTargetFilePath string) error {
 	baseReader, err := filePathReader(filepath)
 	if err != nil {
 		return err