feat(merge): add support for merging from a list of source files

cmd/relspec/merge.go

@@ -47,6 +47,7 @@ var (
 	mergeSourceType    string
 	mergeSourcePath    string
 	mergeSourceConn    string
+	mergeFromList      []string
 	mergeOutputType    string
 	mergeOutputPath    string
 	mergeOutputConn    string
@@ -109,8 +110,9 @@ func init() {
 
 	// Source database flags
 	mergeCmd.Flags().StringVar(&mergeSourceType, "source", "", "Source format (required): dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql")
-	mergeCmd.Flags().StringVar(&mergeSourcePath, "source-path", "", "Source file path (required for file-based formats)")
+	mergeCmd.Flags().StringVar(&mergeSourcePath, "source-path", "", "Source file path (required for file-based formats, mutually exclusive with --from-list)")
 	mergeCmd.Flags().StringVar(&mergeSourceConn, "source-conn", "", "Source connection string (required for pgsql)")
+	mergeCmd.Flags().StringSliceVar(&mergeFromList, "from-list", nil, "Comma-separated list of source file paths to merge (mutually exclusive with --source-path)")
 
 	// Output flags
 	mergeCmd.Flags().StringVar(&mergeOutputType, "output", "", "Output format (required): dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql")
@@ -144,6 +146,11 @@ func runMerge(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("--output format is required")
 	}
 
+	// Validate mutually exclusive source flags
+	if mergeSourcePath != "" && len(mergeFromList) > 0 {
+		return fmt.Errorf("--source-path and --from-list are mutually exclusive")
+	}
+
 	// Validate and expand file paths
 	if mergeTargetType != "pgsql" {
 		if mergeTargetPath == "" {
@@ -157,8 +164,8 @@ func runMerge(cmd *cobra.Command, args []string) error {
 	}
 
 	if mergeSourceType != "pgsql" {
-		if mergeSourcePath == "" {
-			return fmt.Errorf("--source-path is required for %s format", mergeSourceType)
+		if mergeSourcePath == "" && len(mergeFromList) == 0 {
+			return fmt.Errorf("--source-path or --from-list is required for %s format", mergeSourceType)
 		}
 		mergeSourcePath = expandPath(mergeSourcePath)
 	} else if mergeSourceConn == "" {
@@ -189,19 +196,36 @@ func runMerge(cmd *cobra.Command, args []string) error {
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read target database '%s'\n", targetDB.Name)
 	printDatabaseStats(targetDB)
 
-	// Step 2: Read source database
+	// Step 2: Read source database(s)
 	fmt.Fprintf(os.Stderr, "\n[2/3] Reading source database...\n")
 	fmt.Fprintf(os.Stderr, "      Format: %s\n", mergeSourceType)
-	if mergeSourcePath != "" {
-		fmt.Fprintf(os.Stderr, "      Path:   %s\n", mergeSourcePath)
-	}
-	if mergeSourceConn != "" {
-		fmt.Fprintf(os.Stderr, "      Conn:   %s\n", maskPassword(mergeSourceConn))
-	}
 
-	sourceDB, err := readDatabaseForMerge(mergeSourceType, mergeSourcePath, mergeSourceConn, "Source")
-	if err != nil {
-		return fmt.Errorf("failed to read source database: %w", err)
+	var sourceDB *models.Database
+	if len(mergeFromList) > 0 {
+		fmt.Fprintf(os.Stderr, "      Files:  %d file(s)\n", len(mergeFromList))
+		for i, filePath := range mergeFromList {
+			fmt.Fprintf(os.Stderr, "      [%d/%d] %s\n", i+1, len(mergeFromList), filePath)
+			db, readErr := readDatabaseForMerge(mergeSourceType, expandPath(filePath), "", "Source")
+			if readErr != nil {
+				return fmt.Errorf("failed to read source file %s: %w", filePath, readErr)
+			}
+			if sourceDB == nil {
+				sourceDB = db
+			} else {
+				merge.MergeDatabases(sourceDB, db, &merge.MergeOptions{})
+			}
+		}
+	} else {
+		if mergeSourcePath != "" {
+			fmt.Fprintf(os.Stderr, "      Path:   %s\n", mergeSourcePath)
+		}
+		if mergeSourceConn != "" {
+			fmt.Fprintf(os.Stderr, "      Conn:   %s\n", maskPassword(mergeSourceConn))
+		}
+		sourceDB, err = readDatabaseForMerge(mergeSourceType, mergeSourcePath, mergeSourceConn, "Source")
+		if err != nil {
+			return fmt.Errorf("failed to read source database: %w", err)
+		}
 	}
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read source database '%s'\n", sourceDB.Name)
 	printDatabaseStats(sourceDB)