feat: refactor flag for displaying scratch images

.github/copilot-instructions.md

@@ -2,17 +2,23 @@
 
 ## Testing Guidelines
 
+- **TDD Approach**: Follow Red-Green-Refactor cycle for all new features
+  - **Red**: Write failing tests first that describe the desired behavior
+  - **Green**: Write minimal code to make tests pass
+  - **Refactor**: Clean up code while keeping all tests passing
 - **No temporary test files**: Never create standalone test files like "test-*.dockerfile", "quick-test.*", etc.
 - **Use existing test suites**: Add proper test cases to existing test files in the appropriate `*_test.go` files
 - **Follow test patterns**: Use the established testing patterns in the codebase (table-driven tests, proper assertions)
 - **Clean testing**: If testing is needed, extend the existing test suite rather than creating throwaway files
 - **Focus on correct behavior**: Tests should verify expected functionality, not document bugs or regressions
-- **Positive test naming**: Name tests to describe what they verify (e.g., `Test_separateScratchConnections`) rather than what's broken
+- **Test naming**: Name tests to describe what they verify (e.g., `Test_separateScratchConnections`) rather than what's broken
 - **Clear test comments**: Comments should explain what behavior is being tested, not reference historical issues
+- **Comprehensive coverage**: Ensure edge cases, error conditions, and integration scenarios are tested
 
 ## Code Quality
 
 - Follow the existing code style and patterns
 - Use proper error handling
 - Write comprehensive tests for new functionality
 - Maintain backward compatibility unless explicitly breaking changes are needed
+- Always use `make check` for efficient linting and testing - it runs golangci-lint, tests with coverage, and enforces code quality standards in one command

README.md

@@ -154,7 +154,7 @@ Flags:
   -n, --nodesep float           minimum space between two adjacent nodes in the same rank (default 1)
   -o, --output                  output file format, one of: canon, dot, pdf, png, raw, svg (default pdf)
   -r, --ranksep float           minimum separation between ranks (default 0.5)
-      --separate-scratch        create separate nodes for each scratch image instead of collapsing them
+      --scratch                 how to handle scratch images, one of: collapsed, hidden, separated (default collapsed)
   -u, --unflatten uint          stagger length of leaf edges between [1,u] (default 0)
       --version                 display the version of dockerfilegraph
 ```

internal/cmd/root.go

@@ -15,19 +15,19 @@ import (
 )
 
 var (
-	concentrateFlag     bool
-	dpiFlag             uint
-	edgestyleFlag       enum
-	filenameFlag        string
-	layersFlag          bool
-	legendFlag          bool
-	maxLabelLengthFlag  uint
-	nodesepFlag         float64
-	outputFlag          enum
-	ranksepFlag         float64
-	separateScratchFlag bool
-	unflattenFlag       uint
-	versionFlag         bool
+	concentrateFlag    bool
+	dpiFlag            uint
+	edgestyleFlag      enum
+	filenameFlag       string
+	layersFlag         bool
+	legendFlag         bool
+	maxLabelLengthFlag uint
+	nodesepFlag        float64
+	outputFlag         enum
+	ranksepFlag        float64
+	scratchFlag        enum
+	unflattenFlag      uint
+	versionFlag        bool
 )
 
 // dfgWriter is a writer that prints to stdout. When testing, we
@@ -63,12 +63,15 @@ It creates a visual graph representation of the build process.`,
 				return
 			}
 
+			// Determine scratch mode from flag
+			scratchMode := scratchFlag.String()
+
 			// Load and parse the Dockerfile.
 			dockerfile, err := dockerfile2dot.LoadAndParseDockerfile(
 				inputFS,
 				filenameFlag,
 				int(maxLabelLengthFlag),
-				separateScratchFlag,
+				scratchMode,
 			)
 			if err != nil {
 				return
@@ -229,11 +232,11 @@ It creates a visual graph representation of the build process.`,
 		"minimum separation between ranks",
 	)
 
-	rootCmd.Flags().BoolVar(
-		&separateScratchFlag,
-		"separate-scratch",
-		false,
-		"create separate nodes for each scratch image instead of collapsing them",
+	scratchFlag = newEnum("collapsed", "separated", "hidden")
+	rootCmd.Flags().Var(
+		&scratchFlag,
+		"scratch",
+		"how to handle scratch images, one of: "+strings.Join(scratchFlag.AllowedValues(), ", "),
 	)
 
 	rootCmd.Flags().UintVarP(

internal/cmd/root_test.go

@@ -38,7 +38,7 @@ Flags:
   -n, --nodesep float           minimum space between two adjacent nodes in the same rank (default 1)
   -o, --output                  output file format, one of: canon, dot, pdf, png, raw, svg (default pdf)
   -r, --ranksep float           minimum separation between ranks (default 0.5)
-      --separate-scratch        create separate nodes for each scratch image instead of collapsing them
+      --scratch                 how to handle scratch images, one of: collapsed, hidden, separated (default collapsed)
   -u, --unflatten uint          stagger length of leaf edges between [1,u] (default 0)
       --version                 display the version of dockerfilegraph
 `
@@ -492,8 +492,29 @@ It creates a visual graph representation of the build process.
 `,
 		},
 		{
-			name:    "separate scratch flag",
-			cliArgs: []string{"--separate-scratch", "-o", "raw"},
+			name:    "scratch flag collapsed mode",
+			cliArgs: []string{"--scratch", "collapsed", "-o", "raw"},
+			dockerfileContent: "FROM scratch AS app1\nCOPY app1.txt /app1.txt\n\n" +
+				"FROM scratch AS app2\nCOPY app2.txt /app2.txt\n",
+			wantOut:     "Successfully created Dockerfile.raw\n",
+			wantOutFile: "Dockerfile.raw",
+			wantOutFileContent: `digraph G {
+	compound=true;
+	nodesep=1.00;
+	rankdir=LR;
+	ranksep=0.50;
+	external_image_0->stage_0;
+	external_image_0->stage_1;
+	external_image_0 [ color=grey20, fontcolor=grey20, label="scratch", shape=box, style="dashed,rounded", width=2 ];
+	stage_0 [ label="app1", shape=box, style=rounded, width=2 ];
+	stage_1 [ fillcolor=grey90, label="app2", shape=box, style="filled,rounded", width=2 ];
+
+}
+`,
+		},
+		{
+			name:    "scratch flag separated mode",
+			cliArgs: []string{"--scratch", "separated", "-o", "raw"},
 			dockerfileContent: "FROM scratch AS app1\nCOPY app1.txt /app1.txt\n\n" +
 				"FROM scratch AS app2\nCOPY app2.txt /app2.txt\n",
 			wantOut:     "Successfully created Dockerfile.raw\n",
@@ -513,6 +534,30 @@ It creates a visual graph representation of the build process.
 }
 `,
 		},
+		{
+			name:    "scratch flag hidden mode",
+			cliArgs: []string{"--scratch", "hidden", "-o", "raw"},
+			dockerfileContent: "FROM scratch AS app1\nCOPY app1.txt /app1.txt\n\n" +
+				"FROM scratch AS app2\nCOPY app2.txt /app2.txt\n",
+			wantOut:     "Successfully created Dockerfile.raw\n",
+			wantOutFile: "Dockerfile.raw",
+			wantOutFileContent: `digraph G {
+	compound=true;
+	nodesep=1.00;
+	rankdir=LR;
+	ranksep=0.50;
+	stage_0 [ label="app1", shape=box, style=rounded, width=2 ];
+	stage_1 [ fillcolor=grey90, label="app2", shape=box, style="filled,rounded", width=2 ];
+
+}
+`,
+		},
+		{
+			name:         "scratch flag invalid mode",
+			cliArgs:      []string{"--scratch", "invalid", "-o", "raw"},
+			wantErr:      true,
+			wantOutRegex: `invalid argument "invalid" for "--scratch" flag: invalid value: invalid`,
+		},
 	}
 
 	for _, tt := range tests {
@@ -561,40 +606,13 @@ It creates a visual graph representation of the build process.
 			}
 		})
 
-		// Cleanup
+		// Cleanup output files written to real filesystem
 		if tt.wantOutFile != "" {
 			os.Remove(tt.wantOutFile)
 		}
 	}
 }
 
-func TestExecute(t *testing.T) {
-	tests := []test{
-		{
-			name:        "should work",
-			wantOutFile: "Dockerfile.pdf",
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			_ = os.WriteFile("Dockerfile", []byte(dockerfileContent), 0644)
-
-			cmd.Execute()
-
-			if tt.wantOutFile != "" {
-				_, err := os.Stat(tt.wantOutFile)
-				if err != nil {
-					t.Errorf("%s: %v", tt.name, err)
-				}
-			}
-
-			// Cleanup
-			os.Remove("Dockerfile")
-			os.Remove(tt.wantOutFile)
-		})
-	}
-}
-
 func checkWantOut(t *testing.T, tt test, buf *bytes.Buffer) {
 	if tt.wantOut == "" && tt.wantOutRegex == "" {
 		t.Fatalf("Either wantOut or wantOutRegex must be set")