add merge functionality to mg

cmd/mg/cmd/commit.go

@@ -10,7 +10,7 @@ import (
 var commitCmd = &cobra.Command{
 	Use:   "commit",
 	Short: "commit all current repos with the same message",
-	Run: func(cmd *cobra.Command, args []string) {
+	Run: func(_ *cobra.Command, args []string) {
 		fmt.Println("commit called")
 	},
 }

cmd/mg/cmd/import.go

@@ -0,0 +1,61 @@
+package cmd
+
+import (
+	"io"
+	"log"
+	"os"
+
+	"github.com/spf13/cobra"
+	"github.com/taigrr/mg/parse"
+)
+
+var importCmd = &cobra.Command{
+	Use:   "import <file>",
+	Short: "merge a new mgconfig into the current one",
+	Args:  cobra.ExactArgs(1),
+	Run: func(_ *cobra.Command, args []string) {
+		conf := GetConfig()
+		if args[0] == "-" {
+			f, err := io.ReadAll(os.Stdin)
+			if err != nil {
+				log.Println(err)
+				os.Exit(1)
+			}
+			parsed, err := parse.ParseMGConfig(f)
+			if err != nil {
+				log.Println(err)
+				os.Exit(1)
+			}
+			err = conf.Merge(parsed)
+			if err != nil {
+				log.Println(err)
+				os.Exit(1)
+			}
+		} else {
+			f, err := os.ReadFile(args[0])
+			if err != nil {
+				log.Println(err)
+				os.Exit(1)
+			}
+			parsed, err := parse.ParseMGConfig(f)
+			if err != nil {
+				log.Println(err)
+				os.Exit(1)
+			}
+			err = conf.Merge(parsed)
+			if err != nil {
+				log.Println(err)
+				os.Exit(1)
+			}
+		}
+		err := conf.Save()
+		if err != nil {
+			log.Println(err)
+			os.Exit(1)
+		}
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(registerCmd)
+}