feat: Add opt-in validation that PR titles match a single commit (#160)

.github/workflows/lint-pr-title-preview-validateSingleCommit.yml

@@ -21,3 +21,4 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           validateSingleCommit: true
+          validateSingleCommitMatchesPrTitle: true

README.md

@@ -77,6 +77,9 @@ The action works without configuration, however you can provide options for cust
           # merge commit, and it's easy to commit this by mistake. Enable this option
           # to also validate the commit message for one commit PRs.
           validateSingleCommit: true
+          # Related to `validateSingleCommit` you can opt-in to validate that the PR
+          # title matches a single commit to avoid confusion.
+          validateSingleCommitMatchesPrTitle: true
           # If you use Github Enterprise, you can set this to the URL of your server
           githubBaseUrl: https://github.myorg.com/api/v3
 ```

action.yml

@@ -29,6 +29,9 @@ inputs:
   validateSingleCommit:
     description: "When using \"Squash and merge\" on a PR with only one commit, GitHub will suggest using that commit message instead of the PR title for the merge commit, and it's easy to commit this by mistake. Enable this option to also validate the commit message for one commit PRs." 
     required: false
+  validateSingleCommitMatchesPrTitle:
+    description: "Related to `validateSingleCommit` you can opt-in to validate that the PR title matches a single commit to avoid confusion."
+    required: false
   githubBaseUrl:
     description: "If you use Github Enterprise, you can set this to the URL of your server (e.g. https://github.myorg.com/api/v3)"
     required: false

src/index.js

@@ -13,6 +13,7 @@ module.exports = async function run() {
       subjectPattern,
       subjectPatternError,
       validateSingleCommit,
+      validateSingleCommitMatchesPrTitle,
       githubBaseUrl
     } = parseConfig();
 
@@ -98,12 +99,14 @@ module.exports = async function run() {
               );
             }
 
-            const commitTitle =
-              nonMergeCommits[0].commit.message.split('\n')[0];
-            if (commitTitle !== pullRequest.title) {
-              throw new Error(
-                `The pull request has only one (non-merge) commit and in this case Github will use it as the default commit message when merging. The pull request title doesn't match the commit though ("${pullRequest.title}" vs. "${commitTitle}"). Please update the pull request title accordingly to avoid surprises.`
-              );
+            if (validateSingleCommitMatchesPrTitle) {
+              const commitTitle =
+                nonMergeCommits[0].commit.message.split('\n')[0];
+              if (commitTitle !== pullRequest.title) {
+                throw new Error(
+                  `The pull request has only one (non-merge) commit and in this case Github will use it as the default commit message when merging. The pull request title doesn't match the commit though ("${pullRequest.title}" vs. "${commitTitle}"). Please update the pull request title accordingly to avoid surprises.`
+                );
+              }
             }
           }
         }

src/parseConfig.js

@@ -40,6 +40,13 @@ module.exports = function parseConfig() {
     );
   }
 
+  let validateSingleCommitMatchesPrTitle;
+  if (process.env.INPUT_VALIDATESINGLECOMMITMATCHESPRTITLE) {
+    validateSingleCommitMatchesPrTitle = ConfigParser.parseBoolean(
+      process.env.INPUT_VALIDATESINGLECOMMITMATCHESPRTITLE
+    );
+  }
+
   let githubBaseUrl;
   if (process.env.INPUT_GITHUBBASEURL) {
     githubBaseUrl = ConfigParser.parseString(process.env.INPUT_GITHUBBASEURL);
@@ -53,6 +60,7 @@ module.exports = function parseConfig() {
     subjectPattern,
     subjectPatternError,
     validateSingleCommit,
+    validateSingleCommitMatchesPrTitle,
     githubBaseUrl
   };
 };