Use .gitignore as .secretlintignore when necessary

.automation/test/credentials/bad/.gitignore

@@ -0,0 +1 @@
+yolooo/**

.automation/test/credentials/bad/.secretlintignore

@@ -0,0 +1 @@
+yalaaa/**

.automation/test/credentials/good/.gitignore

@@ -0,0 +1 @@
+yoooo/**

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 Note: Can be used with `megalinter/megalinter@beta` in your GitHub Action mega-linter.yml file, or with `megalinter/megalinter:beta` docker image
 
 - New reporter **GITLAB_COMMENT_REPORTER** allowing to post MegaLinter results as comments on Gitlab merge requests
+- secretlint: Use .gitignore as .secretlintignore if --secretlintignore is not defined and .secretlintignore not found ([#1207](https://github.com/megalinter/megalinter/issues/1207))
 - Fix v5 doc deployment when there is a new release ([1190](https://github.com/megalinter/megalinter/issues/1190))
 - Fix issue when using `VALIDATE_ALL_CODEBASE: false` on Azure Pipelines by defining auth header in CI env variable GIT_AUTHORIZATION_BEARER ([#1125](https://github.com/megalinter/megalinter/issues/1125))
 

megalinter/descriptors/credentials.megalinter-descriptor.yml

@@ -5,7 +5,8 @@ descriptor_flavors:
 lint_all_files: true
 linters:
   # SECRETLINT
-  - linter_name: secretlint
+  - class: SecretLintLinter
+    linter_name: secretlint
     linter_url: https://github.com/secretlint/secretlint
     linter_repo: https://github.com/secretlint/secretlint
     linter_banner_image_url: https://github.com/secretlint/secretlint/raw/main/docs/assets/SecretLintLP.png

megalinter/linters/SecretLintLinter.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+"""
+Use secretlint to find secrets in sources
+https://github.com/secretlint/secretlint
+"""
+
+import os
+
+from megalinter import Linter
+
+
+class SecretLintLinter(Linter):
+
+    # Called before linting files
+    def before_lint_files(self):
+        # Use .gitignore as .secretlintignore
+        # only if --secretlintignore is not defined and .secretlintignore not found
+        if "--secretlintignore" not in self.cli_lint_user_args and (
+            os.path.isfile(os.path.join(self.workspace, ".gitignore"))
+            and (not os.path.isfile(os.path.join(self.workspace, ".secretlintignore")))
+        ):
+            self.cli_lint_extra_args += ["--secretlintignore", ".gitignore"]