fix: Improve documentation and refactor tests to cover regex with special characters

Author: philippwaller

README.md

@@ -395,9 +395,15 @@ given regexs.
 
 ```yaml
 files: 
-- "cmd/.*_tests.go"
+- "cmd\\/.*_tests.go"
+- ".*\\/subfolder\\/.*\\.md"
 ```
 
+> **NOTICE** the double backslash (`\\`) in the example above. This GitHub Action is coded in Go (Golang), which means
+> you need to pay special attention to regular expressions (Regex). Special characters need to be escaped with double
+> backslashes. This is because the backslash in Go strings is an escape character and therefore must be escaped itself 
+> to appear as a literal in the regex.
+
 ### Mergeable status (PRs only) <a name="mergeable" />
 
 This condition is satisfied when the [mergeable

cmd/action_test.go

@@ -123,8 +123,8 @@ func TestGetLabelerConfigV1(t *testing.T) {
 			{
 				Label: "TestFileMatch",
 				Files: []string{
-					"cmd/.*.go",
-					"pkg/.*.go",
+					"cmd\\/.*.go",
+					"pkg\\/.*.go",
 				},
 			},
 			{
@@ -262,7 +262,7 @@ func TestGetLabelerConfig2V1(t *testing.T) {
 		},
 		"TestFileMatch": {
 			Label: "TestFileMatch",
-			Files: []string{"cmd/.*.go", "pkg/.*.go"},
+			Files: []string{"cmd\\/.*.go", "pkg\\/.*.go"},
 		},
 	}
 

pkg/labeler_test.go

@@ -334,7 +334,7 @@ func TestHandleEvent(t *testing.T) {
 					{
 						Label: "L",
 						Size: &SizeConfig{
-							ExcludeFiles: []string{"README.md", "new_file", "dependabot.yml"},
+							ExcludeFiles: []string{"README.md", "new_file", "dependabot.yml", "root/sub/test.md"},
 							// our test file has a diff in four files,
 							// including added/removed which have a
 							// slightly trickier diff.  Adding any of
@@ -479,6 +479,24 @@ func TestHandleEvent(t *testing.T) {
 			initialLabels:  []string{},
 			expectedLabels: []string{"Files"},
 		},
+		{
+			event:    "pull_request",
+			payloads: []string{"diff_pr"},
+			name:     "Test escaping in the file condition",
+			config: LabelerConfigV1{
+				Version: 1,
+				Labels: []LabelMatcher{
+					{
+						Label: "Files",
+						Files: []string{
+							"(.*?)\\/(sub|test)\\/.*",
+						},
+					},
+				},
+			},
+			initialLabels:  []string{},
+			expectedLabels: []string{"Files"},
+		},
 		{
 			event:    "pull_request",
 			payloads: []string{"small_pr"},

test_data/config2_v1.yml

@@ -5,5 +5,5 @@ labels:
     title: ".*"
   - label: "TestFileMatch"
     files: 
-    - "cmd/.*.go"
-    - "pkg/.*.go"
+    - "cmd\\/.*.go"
+    - "pkg\\/.*.go"

test_data/config_v1.yml

@@ -15,8 +15,8 @@ labels:
     size-above: 100
   - label: "TestFileMatch"
     files: 
-    - "cmd/.*.go"
-    - "pkg/.*.go"
+    - "cmd\\/.*.go"
+    - "pkg\\/.*.go"
   - label: "Test"
     authors: 
       - "Test1"

test_data/diff_response

@@ -69,3 +69,10 @@ index 0000000..ce01362
 +++ b/new_file
 @@ -0,0 +1 @@
 +hello
+diff --git a/root/sub/test.md b/root/sub/test.md
+index 6c61a60..85aa975 100644
+--- a/root/sub/test.md
++++ b/root/sub/test.md
+@@ -1 +1 @@
+-# Test File
++# Test File !