feat: add isFixupCommit and isMergeCommit properties

This commit adds the `isFixupCommit` and `isMergeCommit`
properties to both Commit and ConventionalCommit classes.

Current implementation is straightforward and only concerns the
commit message subject:

- Fixup: subject starts with `fixup!`
- Merge: support for default merge commit message patterns of
         GitHub, BitBucket and GitLab

These properties can be used to (for example) ignore Conventional
Commit message validation for these types of commits.

Implements #33

src/commit.ts

@@ -20,6 +20,11 @@ export interface IStringDataSourceOptions {
   message: string;
 }
 
+/**
+ * Name and Date type
+ */
+export type NameAndDateType = { name: string; date: Date };
+
 /**
  * Commit information
  * @interface ICommit
@@ -32,13 +37,17 @@ export interface IStringDataSourceOptions {
  * @internal
  */
 export interface ICommit {
-  author?: { name: string; date: Date };
-  committer?: { name: string; date: Date };
+  author?: NameAndDateType;
+  committer?: NameAndDateType;
   hash: string;
   raw: string;
   subject: string;
   body?: string;
   footer?: Record<string, string>;
+  attributes: {
+    isFixup: boolean;
+    isMerge: boolean;
+  };
 }
 
 const TRAILER_REGEX = /^((BREAKING CHANGE:)|([\w-]+(:| #))|([ \t]+)\w*)/i;
@@ -120,6 +129,12 @@ export class Commit {
   get raw(): string {
     return this._commit.raw;
   }
+  get isFixupCommit(): boolean {
+    return this._commit.attributes.isFixup;
+  }
+  get isMergeCommit(): boolean {
+    return this._commit.attributes.isMerge;
+  }
 
   toJSON(): ICommit {
     return this._commit;
@@ -176,6 +191,24 @@ export function getFooterElementsFromParagraph(
   return Object.keys(result).length > 0 ? result : undefined;
 }
 
+/**
+ * Checks if the provided subject is a common (default) merge pattern.
+ * Currently supported:
+ * - GitHub
+ * - BitBucket
+ * - GitLab
+ *
+ * @param subject The subject to check
+ * @returns True if the subject is a common merge pattern, false otherwise
+ */
+function subjectIsMergePattern(subject: string): boolean {
+  const githubMergeRegex = /^Merge pull request #(\d+) from (.*)$/;
+  const bitbucketMergeRegex = /^Merged in (.*) \(pull request #(\d+)\)$/;
+  const gitlabMergeRegex = /^Merge branch '(.*?)' into '(.*?)'$/;
+
+  return githubMergeRegex.test(subject) || bitbucketMergeRegex.test(subject) || gitlabMergeRegex.test(subject);
+}
+
 /**
  * Parses the provided commit message (full message, not just the subject) into
  * a Commit object.
@@ -187,6 +220,10 @@ export function parseCommitMessage(message: string): {
   subject: string;
   body?: string;
   footer?: Record<string, string>;
+  attributes: {
+    isFixup: boolean;
+    isMerge: boolean;
+  };
 } {
   const isTrailerOnly = (message: string): boolean =>
     message.split(/\r?\n/).every(line => {
@@ -208,12 +245,20 @@ export function parseCommitMessage(message: string): {
     if (body === "") body = undefined;
   }
 
+  const subject = paragraphs[0].trim();
+  const isFixup = subject.toLowerCase().startsWith("fixup!");
+  const isMerge = subjectIsMergePattern(subject);
+
   return {
-    subject: paragraphs[0].trim(),
-    body: body,
+    subject,
+    body,
     footer: getFooterElementsFromParagraph(footer ?? "")?.reduce((acc, cur) => {
       acc[cur.key] = cur.value;
       return acc;
     }, {} as Record<string, string>),
+    attributes: {
+      isFixup,
+      isMerge,
+    },
   };
 }

src/conventionalCommit.ts

@@ -169,6 +169,14 @@ export class ConventionalCommit {
     );
   }
 
+  // Attributes
+  get isFixupCommit(): boolean {
+    return this._raw.commit.isFixupCommit;
+  }
+  get isMergeCommit(): boolean {
+    return this._raw.commit.isMergeCommit;
+  }
+
   // Raw
   get raw(): string {
     return this._raw.commit.raw;
@@ -201,6 +209,10 @@ export class ConventionalCommit {
         errors: this.errors,
         warnings: this.warnings,
       },
+      attributes: {
+        isFixup: this.isFixupCommit,
+        isMerge: this.isMergeCommit,
+      },
     };
   }
 

src/git.ts

@@ -9,20 +9,7 @@ import * as path from "path";
 import * as zlib from "zlib";
 
 import * as ccommit from "./commit";
-
-/** @internal */
-type NameAndDateType = { name: string; date: Date };
-
-/** @internal */
-type GitCommitType = {
-  hash: string;
-  raw: string;
-  author?: NameAndDateType;
-  committer?: NameAndDateType;
-  subject: string;
-  body?: string;
-  footer?: Record<string, string>;
-};
+import { ICommit, NameAndDateType } from "./commit";
 
 /** @internal */
 export const gitObjectFolder = ".git/objects";
@@ -71,30 +58,25 @@ function getValueFromKey(commit: string, key: string): string | undefined {
  * @param hash Commit hash
  * @returns Commit object
  */
-function parseCommitMessage(commit: string, hash: string): GitCommitType {
+function parseCommitMessage(commit: string, hash: string): ICommit {
   const author = extractNameAndDate(getValueFromKey(commit, "author"));
   const committer = extractNameAndDate(getValueFromKey(commit, "committer"));
+
   const raw = commit
     .split(/^[\r\n]+/m)
     .splice(1)
     .join("\n")
     .trim();
 
-  return {
-    raw,
-    hash: hash,
-    author: author,
-    committer: committer,
-    ...ccommit.parseCommitMessage(raw),
-  };
+  return { raw, hash, author, committer, ...ccommit.parseCommitMessage(raw) };
 }
 
 /**
  * Reads a (local) commit message from the .git/objects folder
  * @param hash Hash of the commit to read
  * @returns Commit object or undefined if the commit could not be found in the local repository
  */
-function getCommitFromLocalObjects(hash: string, rootPath: string): ccommit.ICommit | undefined {
+function getCommitFromLocalObjects(hash: string, rootPath: string): ICommit | undefined {
   const objectPath = path.join(rootPath, gitObjectFolder, hash.substring(0, 2), "/", hash.substring(2));
   if (!fs.existsSync(objectPath)) return undefined;
 
@@ -108,7 +90,7 @@ function getCommitFromLocalObjects(hash: string, rootPath: string): ccommit.ICom
  * @param rootPath Path to the git repository
  * @returns Commit object or undefined if the commit could not be found in the pack files
  */
-function getCommitFromPackFile(hash: string, rootPath: string): ccommit.ICommit | undefined {
+function getCommitFromPackFile(hash: string, rootPath: string): ICommit | undefined {
   for (const entry of fs.readdirSync(path.join(rootPath, gitObjectFolder, "pack"))) {
     const filePath = path.join(rootPath, gitObjectFolder, "pack", entry);
     if (path.extname(filePath) !== ".idx") continue;
@@ -127,7 +109,7 @@ function getCommitFromPackFile(hash: string, rootPath: string): ccommit.ICommit
  * @returns Commit object
  * @internal
  */
-export function getCommitFromHash(hash: string, rootPath: string): ccommit.ICommit {
+export function getCommitFromHash(hash: string, rootPath: string): ICommit {
   if (!fs.existsSync(path.join(rootPath, gitObjectFolder)))
     throw new Error(`Invalid git folder specified (${path.join(rootPath, gitObjectFolder)})`);
 

src/index.ts

@@ -4,5 +4,7 @@
  */
 
 export { Commit } from "./commit";
+export type { NameAndDateType } from "./commit";
+
 export { ConventionalCommit } from "./conventionalCommit";
 export type { IConventionalCommitOptions } from "./conventionalCommit";

test/conventional_commit.test.ts → test/conventionalCommit.test.ts

@@ -285,3 +285,29 @@ describe("Commit message ends at first comment (#)", () => {
     expect(commit.breaking).toBe(test.breaking);
   });
 });
+
+describe("Fixup commits", () => {
+  const tests = [{ message: "fixup! add feat: some feature" }, { message: "fixup! fixup! add feat: some feature" }];
+
+  it.each(tests)("$message", test => {
+    const commit = ConventionalCommit.fromString({ hash: "01ab2cd3", message: test.message });
+
+    expect(commit.isValid).toBe(false);
+    expect(commit.isFixupCommit).toBe(true);
+  });
+});
+
+describe("Merge commits", () => {
+  const tests = [
+    { message: "Merge pull request #123 from some-branch/feature/branch" },
+    { message: "Merged in ci/some-branch (pull request #123)" },
+    { message: "Merge branch 'ci/some-branch' into 'main'" },
+  ];
+
+  it.each(tests)("$message", test => {
+    const commit = ConventionalCommit.fromString({ hash: "01ab2cd3", message: test.message });
+
+    expect(commit.isValid).toBe(false);
+    expect(commit.isMergeCommit).toBe(true);
+  });
+});

test/git.test.ts

@@ -3,6 +3,7 @@
  * SPDX-License-Identifier: MIT
  */
 
+import { ICommit } from "../src/commit";
 import * as git from "../src/git";
 import { Commit } from "../src/index";
 
@@ -38,7 +39,8 @@ in .git/objects. Rationale: remove any need for external dependencies
 
 Calling \`getCommitMessage(...)\` will return a standard ICommit object`,
         footer: undefined,
-      } as Commit,
+        attributes: { isFixup: false, isMerge: false },
+      } as ICommit,
     });
   });
 
@@ -59,7 +61,8 @@ Calling \`getCommitMessage(...)\` will return a standard ICommit object`,
         subject: "Initial commit",
         body: undefined,
         footer: undefined,
-      } as Commit,
+        attributes: { isFixup: false, isMerge: false },
+      } as ICommit,
     });
   });