fix: adjust previous commit id on merge commits (#5950)

- When a commit is a merge commit, adjust the revision so that it
  selects the correct parent.
- Add relevant tests.
- Extract the logic to initialize a Git repository for tests in a
  dedicated function.

Fix #5941

Makefile

@@ -4,7 +4,7 @@
 all: info docker test ## Run all targets.
 
 .PHONY: test
-test: info validate-container-image-labels docker-build-check docker-dev-container-build-check test-lib inspec lint-codebase test-default-config-files test-actions-runner-debug test-actions-steps-debug test-runner-debug test-find lint-subset-files test-custom-ssl-cert test-non-default-workdir test-git-flags test-non-default-home-directory test-git-initial-commit test-log-level test-use-find-and-ignore-gitignored-files test-linters-expect-failure-log-level-notice test-bash-exec-library-expect-success test-bash-exec-library-expect-failure test-save-super-linter-output test-save-super-linter-output-custom-path test-save-super-linter-custom-summary test-linters ## Run the test suite
+test: info validate-container-image-labels docker-build-check docker-dev-container-build-check test-lib inspec lint-codebase test-default-config-files test-actions-runner-debug test-actions-steps-debug test-runner-debug test-find lint-subset-files test-custom-ssl-cert test-non-default-workdir test-git-flags test-non-default-home-directory test-git-initial-commit test-git-merge-commit-push test-log-level test-use-find-and-ignore-gitignored-files test-linters-expect-failure-log-level-notice test-bash-exec-library-expect-success test-bash-exec-library-expect-failure test-save-super-linter-output test-save-super-linter-output-custom-path test-save-super-linter-custom-summary test-linters ## Run the test suite
 
 # if this session isn't interactive, then we don't want to allocate a
 # TTY, which would fail, but if it is interactive, we do want to attach
@@ -425,6 +425,13 @@ test-git-initial-commit: ## Run super-linter against a repository that only has
 		"run_test_case_git_initial_commit" \
 		"$(IMAGE)"
 
+.PHONY: test-git-merge-commit-push
+test-git-merge-commit-push: ## Run super-linter against a repository that has merge commits on a push event
+	$(CURDIR)/test/run-super-linter-tests.sh \
+		$(SUPER_LINTER_TEST_CONTAINER_URL) \
+		"run_test_case_merge_commit_push" \
+		"$(IMAGE)"
+
 .PHONY: test-use-find-and-ignore-gitignored-files
 test-use-find-and-ignore-gitignored-files: ## Run super-linter with USE_FIND_ALGORITHM=true and IGNORE_GITIGNORED_FILES=true
 	$(CURDIR)/test/run-super-linter-tests.sh \

lib/linter.sh

@@ -410,8 +410,31 @@ GetGitHubVars() {
 
         # Ref: https://docs.github.com/en/actions/learn-github-actions/contexts#github-context
         debug "Get the hash of the commit to start the diff from from Git because the GitHub push event payload may not contain references to base_ref or previous commit."
+
+        debug "Check if the commit is a merge commit by checking if it has more than one parent"
+        local GIT_COMMIT_PARENTS_COUNT
+        GIT_COMMIT_PARENTS_COUNT=$(git -C "${GITHUB_WORKSPACE}" rev-list --parents -n 1 "${GITHUB_SHA}" | wc -w)
+        debug "Git commit parents count (GIT_COMMIT_PARENTS_COUNT): ${GIT_COMMIT_PARENTS_COUNT}"
+        GIT_COMMIT_PARENTS_COUNT=$((GIT_COMMIT_PARENTS_COUNT - 1))
+        debug "Subtract 1 from GIT_COMMIT_PARENTS_COUNT to get the actual number of merge parents because the count includes the commit itself. GIT_COMMIT_PARENTS_COUNT: ${GIT_COMMIT_PARENTS_COUNT}"
+
+        # Ref: https://git-scm.com/docs/git-rev-parse#Documentation/git-rev-parse.txt
+        local GIT_BEFORE_SHA_HEAD="HEAD"
+        if [ ${GIT_COMMIT_PARENTS_COUNT} -gt 1 ]; then
+          debug "${GITHUB_SHA} is a merge commit because it has more than one parent."
+          GIT_BEFORE_SHA_HEAD="${GIT_BEFORE_SHA_HEAD}^2"
+          debug "Add the suffix to GIT_BEFORE_SHA_HEAD to get the second parent of the merge commit: ${GIT_BEFORE_SHA_HEAD}"
+          GITHUB_PUSH_COMMIT_COUNT=$((GITHUB_PUSH_COMMIT_COUNT - 1))
+          debug "Remove one commit from GITHUB_PUSH_COMMIT_COUNT to account for the merge commit. GITHUB_PUSH_COMMIT_COUNT: ${GITHUB_PUSH_COMMIT_COUNT}"
+        else
+          debug "${GITHUB_SHA} is not a merge commit because it has a single parent. No need to add the parent identifier (^) to the revision indicator because it's implicitly set to ^1 when there's only one parent."
+        fi
+
+        GIT_BEFORE_SHA_HEAD="${GIT_BEFORE_SHA_HEAD}~${GITHUB_PUSH_COMMIT_COUNT}"
+        debug "GIT_BEFORE_SHA_HEAD: ${GIT_BEFORE_SHA_HEAD}"
+
         # shellcheck disable=SC2086  # We checked that GITHUB_PUSH_COMMIT_COUNT is an integer
-        if ! GITHUB_BEFORE_SHA=$(git -C "${GITHUB_WORKSPACE}" rev-parse HEAD~${GITHUB_PUSH_COMMIT_COUNT}); then
+        if ! GITHUB_BEFORE_SHA=$(git -C "${GITHUB_WORKSPACE}" rev-parse ${GIT_BEFORE_SHA_HEAD}); then
           fatal "Failed to initialize GITHUB_BEFORE_SHA for a push event. Output: ${GITHUB_BEFORE_SHA}"
         fi
 

test/data/github-event/github-event-push-merge-commit.json

@@ -0,0 +1,246 @@
+{
+  "after": "cc62b30b91677b695d3929d6352e7bb541e5ed8c",
+  "base_ref": null,
+  "before": "dc27afaa1f4d1b098cbf7602b82de312d20fa481",
+  "commits": [
+    {
+      "author": {
+        "email": "lae@lae.is",
+        "name": "lae",
+        "username": "lae"
+      },
+      "committer": {
+        "email": "lae@lae.is",
+        "name": "lae",
+        "username": "lae"
+      },
+      "distinct": false,
+      "id": "74e0339cc37cf77494b723107bd803f6adfd0d9f",
+      "message": "add README",
+      "timestamp": "2024-07-31T06:25:36+09:00",
+      "tree_id": "807fa49be3c439afd7723e7e3a8fea2103bd7368",
+      "url": "https://github.com/amplify-security/sl-repro-5941/commit/74e0339cc37cf77494b723107bd803f6adfd0d9f"
+    },
+    {
+      "author": {
+        "email": "lae@lae.is",
+        "name": "lae",
+        "username": "lae"
+      },
+      "committer": {
+        "email": "lae@lae.is",
+        "name": "lae",
+        "username": "lae"
+      },
+      "distinct": false,
+      "id": "6a887dce059f8bb8bbe597770fd23f88478d6917",
+      "message": "update README",
+      "timestamp": "2024-07-31T06:28:50+09:00",
+      "tree_id": "d12d6bf3200d2bf95052ed41ad0f0c7c58c91dc2",
+      "url": "https://github.com/amplify-security/sl-repro-5941/commit/6a887dce059f8bb8bbe597770fd23f88478d6917"
+    },
+    {
+      "author": {
+        "email": "lae@lae.is",
+        "name": "lae",
+        "username": "lae"
+      },
+      "committer": {
+        "email": "lae@lae.is",
+        "name": "lae",
+        "username": "lae"
+      },
+      "distinct": false,
+      "id": "03571b8e42247c5451b7d1cca3e2eccedb5bc4d3",
+      "message": "update README",
+      "timestamp": "2024-07-31T06:31:01+09:00",
+      "tree_id": "807fa49be3c439afd7723e7e3a8fea2103bd7368",
+      "url": "https://github.com/amplify-security/sl-repro-5941/commit/03571b8e42247c5451b7d1cca3e2eccedb5bc4d3"
+    },
+    {
+      "author": {
+        "email": "lae@users.noreply.github.com",
+        "name": "lae",
+        "username": "lae"
+      },
+      "committer": {
+        "email": "noreply@github.com",
+        "name": "GitHub",
+        "username": "web-flow"
+      },
+      "distinct": true,
+      "id": "cc62b30b91677b695d3929d6352e7bb541e5ed8c",
+      "message": "Merge pull request #1 from amplify-security/feature/readme\nadd README",
+      "timestamp": "2024-07-31T06: 33: 25+09: 00",
+      "tree_id": "807fa49be3c439afd7723e7e3a8fea2103bd7368",
+      "url": "https://github.com/amplify-security/sl-repro-5941/commit/cc62b30b91677b695d3929d6352e7bb541e5ed8c"
+    }
+  ],
+  "compare": "https://github.com/amplify-security/sl-repro-5941/compare/dc27afaa1f4d...cc62b30b9167",
+  "created": false,
+  "deleted": false,
+  "forced": false,
+  "head_commit": {
+    "author": {
+      "email": "lae@users.noreply.github.com",
+      "name": "lae",
+      "username": "lae"
+    },
+    "committer": {
+      "email": "noreply@github.com",
+      "name": "GitHub",
+      "username": "web-flow"
+    },
+    "distinct": true,
+    "id": "cc62b30b91677b695d3929d6352e7bb541e5ed8c",
+    "message": "Merge pull request #1 from amplify-security/feature/readme\nadd README",
+    "timestamp": "2024-07-31T06: 33: 25+09: 00",
+    "tree_id": "807fa49be3c439afd7723e7e3a8fea2103bd7368",
+    "url": "https://github.com/amplify-security/sl-repro-5941/commit/cc62b30b91677b695d3929d6352e7bb541e5ed8c"
+  },
+  "organization": {
+    "avatar_url": "https://avatars.githubusercontent.com/u/105519894?v=4",
+    "description": "",
+    "events_url": "https://api.github.com/orgs/amplify-security/events",
+    "hooks_url": "https://api.github.com/orgs/amplify-security/hooks",
+    "id": 105519894,
+    "issues_url": "https://api.github.com/orgs/amplify-security/issues",
+    "login": "amplify-security",
+    "members_url": "https://api.github.com/orgs/amplify-security/members{/member}",
+    "node_id": "O_kgDOBkobFg",
+    "public_members_url": "https://api.github.com/orgs/amplify-security/public_members{/member}",
+    "repos_url": "https://api.github.com/orgs/amplify-security/repos",
+    "url": "https://api.github.com/orgs/amplify-security"
+  },
+  "pusher": {
+    "email": "lae@users.noreply.github.com",
+    "name": "lae"
+  },
+  "ref": "refs/heads/main",
+  "repository": {
+    "allow_forking": true,
+    "archive_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/{archive_format}{/ref}",
+    "archived": false,
+    "assignees_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/assignees{/user}",
+    "blobs_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/git/blobs{/sha}",
+    "branches_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/branches{/branch}",
+    "clone_url": "https://github.com/amplify-security/sl-repro-5941.git",
+    "collaborators_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/collaborators{/collaborator}",
+    "comments_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/comments{/number}",
+    "commits_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/commits{/sha}",
+    "compare_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/compare/{base}...{head}",
+    "contents_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/contents/{+path}",
+    "contributors_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/contributors",
+    "created_at": 1722374504,
+    "custom_properties": {},
+    "default_branch": "main",
+    "deployments_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/deployments",
+    "description": null,
+    "disabled": false,
+    "downloads_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/downloads",
+    "events_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/events",
+    "fork": false,
+    "forks": 0,
+    "forks_count": 0,
+    "forks_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/forks",
+    "full_name": "amplify-security/sl-repro-5941",
+    "git_commits_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/git/commits{/sha}",
+    "git_refs_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/git/refs{/sha}",
+    "git_tags_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/git/tags{/sha}",
+    "git_url": "git://github.com/amplify-security/sl-repro-5941.git",
+    "has_discussions": false,
+    "has_downloads": true,
+    "has_issues": true,
+    "has_pages": false,
+    "has_projects": true,
+    "has_wiki": true,
+    "homepage": null,
+    "hooks_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/hooks",
+    "html_url": "https://github.com/amplify-security/sl-repro-5941",
+    "id": 835952240,
+    "is_template": false,
+    "issue_comment_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/issues/comments{/number}",
+    "issue_events_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/issues/events{/number}",
+    "issues_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/issues{/number}",
+    "keys_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/keys{/key_id}",
+    "labels_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/labels{/name}",
+    "language": null,
+    "languages_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/languages",
+    "license": null,
+    "master_branch": "main",
+    "merges_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/merges",
+    "milestones_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/milestones{/number}",
+    "mirror_url": null,
+    "name": "sl-repro-5941",
+    "node_id": "R_kgDOMdOecA",
+    "notifications_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/notifications{?since,all,participating}",
+    "open_issues": 0,
+    "open_issues_count": 0,
+    "organization": "amplify-security",
+    "owner": {
+      "avatar_url": "https://avatars.githubusercontent.com/u/105519894?v=4",
+      "email": null,
+      "events_url": "https://api.github.com/users/amplify-security/events{/privacy}",
+      "followers_url": "https://api.github.com/users/amplify-security/followers",
+      "following_url": "https://api.github.com/users/amplify-security/following{/other_user}",
+      "gists_url": "https://api.github.com/users/amplify-security/gists{/gist_id}",
+      "gravatar_id": "",
+      "html_url": "https://github.com/amplify-security",
+      "id": 105519894,
+      "login": "amplify-security",
+      "name": "amplify-security",
+      "node_id": "O_kgDOBkobFg",
+      "organizations_url": "https://api.github.com/users/amplify-security/orgs",
+      "received_events_url": "https://api.github.com/users/amplify-security/received_events",
+      "repos_url": "https://api.github.com/users/amplify-security/repos",
+      "site_admin": false,
+      "starred_url": "https://api.github.com/users/amplify-security/starred{/owner}{/repo}",
+      "subscriptions_url": "https://api.github.com/users/amplify-security/subscriptions",
+      "type": "Organization",
+      "url": "https://api.github.com/users/amplify-security"
+    },
+    "private": false,
+    "pulls_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/pulls{/number}",
+    "pushed_at": 1722375205,
+    "releases_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/releases{/id}",
+    "size": 0,
+    "ssh_url": "git@github.com:amplify-security/sl-repro-5941.git",
+    "stargazers": 0,
+    "stargazers_count": 0,
+    "stargazers_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/stargazers",
+    "statuses_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/statuses/{sha}",
+    "subscribers_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/subscribers",
+    "subscription_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/subscription",
+    "svn_url": "https://github.com/amplify-security/sl-repro-5941",
+    "tags_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/tags",
+    "teams_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/teams",
+    "topics": [],
+    "trees_url": "https://api.github.com/repos/amplify-security/sl-repro-5941/git/trees{/sha}",
+    "updated_at": "2024-07-30T21:24:53Z",
+    "url": "https://github.com/amplify-security/sl-repro-5941",
+    "visibility": "public",
+    "watchers": 0,
+    "watchers_count": 0,
+    "web_commit_signoff_required": false
+  },
+  "sender": {
+    "avatar_url": "https://avatars.githubusercontent.com/u/1318013?v=4",
+    "events_url": "https://api.github.com/users/lae/events{/privacy}",
+    "followers_url": "https://api.github.com/users/lae/followers",
+    "following_url": "https://api.github.com/users/lae/following{/other_user}",
+    "gists_url": "https://api.github.com/users/lae/gists{/gist_id}",
+    "gravatar_id": "",
+    "html_url": "https://github.com/lae",
+    "id": 1318013,
+    "login": "lae",
+    "node_id": "MDQ6VXNlcjEzMTgwMTM=",
+    "organizations_url": "https://api.github.com/users/lae/orgs",
+    "received_events_url": "https://api.github.com/users/lae/received_events",
+    "repos_url": "https://api.github.com/users/lae/repos",
+    "site_admin": false,
+    "starred_url": "https://api.github.com/users/lae/starred{/owner}{/repo}",
+    "subscriptions_url": "https://api.github.com/users/lae/subscriptions",
+    "type": "User",
+    "url": "https://api.github.com/users/lae"
+  }
+}

test/run-super-linter-tests.sh

@@ -62,33 +62,74 @@ run_test_case_bash_exec_library_expect_success() {
   COMMAND_TO_RUN+=(-e BASH_EXEC_IGNORE_LIBRARIES="true")
 }
 
-run_test_case_git_initial_commit() {
+initialize_git_repository_and_test_args() {
-  local GIT_REPOSITORY_PATH
+  local GIT_REPOSITORY_PATH="${1}"
-  GIT_REPOSITORY_PATH="$(mktemp -d)"
   # shellcheck disable=SC2064 # Once the path is set, we don't expect it to change
   trap "rm -fr '${GIT_REPOSITORY_PATH}'" EXIT
 
+  local GITHUB_EVENT_FILE_PATH="${2}"
+
   git -C "${GIT_REPOSITORY_PATH}" init --initial-branch="${DEFAULT_BRANCH}"
   git -C "${GIT_REPOSITORY_PATH}" config user.name "Super-linter Test"
   git -C "${GIT_REPOSITORY_PATH}" config user.email "super-linter-test@example.com"
-  cp -v test/data/github-event/github-event-push.json "${GIT_REPOSITORY_PATH}/"
+  # Put an arbitrary JSON file in the repository to trigger some validation
+  cp -v "${GITHUB_EVENT_FILE_PATH}" "${GIT_REPOSITORY_PATH}/"
   git -C "${GIT_REPOSITORY_PATH}" add .
   git -C "${GIT_REPOSITORY_PATH}" commit -m "feat: initial commit"
 
-  local TEST_GITHUB_SHA
-  TEST_GITHUB_SHA="$(git -C "${GIT_REPOSITORY_PATH}" rev-parse HEAD)"
-
   RUN_LOCAL=false
   SUPER_LINTER_WORKSPACE="${GIT_REPOSITORY_PATH}"
   COMMAND_TO_RUN+=(-e GITHUB_WORKSPACE="/tmp/lint")
   COMMAND_TO_RUN+=(-e GITHUB_EVENT_NAME="push")
-  COMMAND_TO_RUN+=(-e GITHUB_EVENT_PATH="/tmp/lint/github-event-push.json")
+  COMMAND_TO_RUN+=(-e GITHUB_EVENT_PATH="/tmp/lint/$(basename "${GITHUB_EVENT_FILE_PATH}")")
-  COMMAND_TO_RUN+=(-e GITHUB_SHA="${TEST_GITHUB_SHA}")
   COMMAND_TO_RUN+=(-e MULTI_STATUS=false)
   COMMAND_TO_RUN+=(-e VALIDATE_ALL_CODEBASE=false)
   COMMAND_TO_RUN+=(-e VALIDATE_JSON=true)
 }
 
+run_test_case_git_initial_commit() {
+  local GIT_REPOSITORY_PATH
+  GIT_REPOSITORY_PATH="$(mktemp -d)"
+
+  initialize_git_repository_and_test_args "${GIT_REPOSITORY_PATH}" "test/data/github-event/github-event-push.json"
+
+  local TEST_GITHUB_SHA
+  TEST_GITHUB_SHA="$(git -C "${GIT_REPOSITORY_PATH}" rev-parse HEAD)"
+  COMMAND_TO_RUN+=(-e GITHUB_SHA="${TEST_GITHUB_SHA}")
+}
+
+run_test_case_merge_commit_push() {
+  local GIT_REPOSITORY_PATH
+  GIT_REPOSITORY_PATH="$(mktemp -d)"
+
+  initialize_git_repository_and_test_args "${GIT_REPOSITORY_PATH}" "test/data/github-event/github-event-push-merge-commit.json"
+
+  local NEW_BRANCH_NAME="branch-1"
+  git -C "${GIT_REPOSITORY_PATH}" switch --create "${NEW_BRANCH_NAME}"
+  cp -v "test/data/github-event/github-event-push-merge-commit.json" "${GIT_REPOSITORY_PATH}/new-file-1.json"
+  git -C "${GIT_REPOSITORY_PATH}" add .
+  git -C "${GIT_REPOSITORY_PATH}" commit -m "feat: add new file 1"
+  cp -v "test/data/github-event/github-event-push-merge-commit.json" "${GIT_REPOSITORY_PATH}/new-file-2.json"
+  git -C "${GIT_REPOSITORY_PATH}" add .
+  git -C "${GIT_REPOSITORY_PATH}" commit -m "feat: add new file 2"
+  cp -v "test/data/github-event/github-event-push-merge-commit.json" "${GIT_REPOSITORY_PATH}/new-file-3.json"
+  git -C "${GIT_REPOSITORY_PATH}" add .
+  git -C "${GIT_REPOSITORY_PATH}" commit -m "feat: add new file 3"
+  git -C "${GIT_REPOSITORY_PATH}" switch "${DEFAULT_BRANCH}"
+  # Force the creation of a merge commit
+  git -C "${GIT_REPOSITORY_PATH}" merge \
+    -m "Merge commit" \
+    --no-ff \
+    "${NEW_BRANCH_NAME}"
+  git -C "${GIT_REPOSITORY_PATH}" branch -d "${NEW_BRANCH_NAME}"
+
+  git -C "${GIT_REPOSITORY_PATH}" log --all --graph --abbrev-commit --decorate --format=oneline
+
+  local TEST_GITHUB_SHA
+  TEST_GITHUB_SHA="$(git -C "${GIT_REPOSITORY_PATH}" rev-parse HEAD)"
+  COMMAND_TO_RUN+=(-e GITHUB_SHA="${TEST_GITHUB_SHA}")
+}
+
 run_test_case_use_find_and_ignore_gitignored_files() {
   ignore_test_cases
   COMMAND_TO_RUN+=(-e IGNORE_GITIGNORED_FILES=true)