feat: add config option to enable Signed-off-by in commit messages

Some organizations require Signed-off-by trailers in commit
messages (e.g. for Developer Certificate of Origin). GitHub has a
setting to enable this when authoring changes from the Web UI.
This patch adds a similar setting for DecapCMS.

Closes: #7730

Author: emersion

packages/decap-cms-core/index.d.ts

@@ -364,6 +364,7 @@ declare module 'decap-cms-core' {
     auth_type?: 'implicit' | 'pkce';
     cms_label_prefix?: string;
     squash_merges?: boolean;
+    signoff_commits?: boolean;
     proxy_url?: string;
     commit_messages?: {
       create?: string;

packages/decap-cms-core/src/backend.ts

@@ -1178,6 +1178,7 @@ export class Backend {
         path,
         authorLogin: user.login,
         authorName: user.name,
+        authorEmail: user.email,
       },
       user.useOpenAuthoring,
     );
@@ -1253,6 +1254,7 @@ export class Backend {
           path: file.path,
           authorLogin: user.login,
           authorName: user.name,
+          authorEmail: user.email,
         },
         user.useOpenAuthoring,
       ),
@@ -1279,6 +1281,7 @@ export class Backend {
         path,
         authorLogin: user.login,
         authorName: user.name,
+        authorEmail: user.email,
       },
       user.useOpenAuthoring,
     );
@@ -1303,6 +1306,7 @@ export class Backend {
         path,
         authorLogin: user.login,
         authorName: user.name,
+        authorEmail: user.email,
       },
       user.useOpenAuthoring,
     );

packages/decap-cms-core/src/lib/__tests__/formatters.spec.js

@@ -247,6 +247,27 @@ describe('formatters', () => {
         'Ignoring unknown variable “author-email” in open authoring message template.',
       );
     });
+
+    it('should return commit with trailer when signoff_commits is enabled', () => {
+      const collection = Map({ label_singular: 'Collection' });
+      const config = {
+        backend: {
+          signoff_commits: true,
+        },
+      };
+
+      expect(
+        commitMessageFormatter('create', config, {
+          slug: 'doc-slug',
+          path: 'file-path',
+          collection,
+          authorName: 'Test User',
+          authorEmail: 'test-user@example.org',
+        }),
+      ).toEqual(
+        'Create Collection “doc-slug”\n\nSigned-off-by: Test User <test-user@example.org>\n',
+      );
+    });
   });
 
   describe('prepareSlug', () => {

packages/decap-cms-core/src/lib/formatters.ts

@@ -44,16 +44,28 @@ type Options = {
   collection?: Collection;
   authorLogin?: string;
   authorName?: string;
+  authorEmail?: string;
 };
 
 export function commitMessageFormatter(
   type: keyof typeof commitMessageTemplates,
   config: CmsConfig,
-  { slug, path, collection, authorLogin, authorName }: Options,
+  { slug, path, collection, authorLogin, authorName, authorEmail }: Options,
   isOpenAuthoring?: boolean,
 ) {
   const templates = { ...commitMessageTemplates, ...(config.backend.commit_messages || {}) };
 
+  let trailers = '';
+  if (config.backend.signoff_commits) {
+    if (!authorName) {
+      console.warn('Option signoff_commits is enabled, but author name is unknown');
+    } else if (!authorEmail) {
+      console.warn('Option signoff_commits is enabled, but author email is unknown');
+    } else {
+      trailers = `\n\nSigned-off-by: ${authorName} <${authorEmail}>\n`;
+    }
+  }
+
   const commitMessage = templates[type].replace(variableRegex, (_, variable) => {
     switch (variable) {
       case 'slug':
@@ -73,7 +85,7 @@ export function commitMessageFormatter(
   });
 
   if (!isOpenAuthoring) {
-    return commitMessage;
+    return commitMessage + trailers;
   }
 
   const message = templates.openAuthoring.replace(variableRegex, (_, variable) => {
@@ -90,7 +102,7 @@ export function commitMessageFormatter(
     }
   });
 
-  return message;
+  return message + trailers;
 }
 
 export function prepareSlug(slug: string) {

packages/decap-cms-core/src/types/redux.ts

@@ -377,6 +377,7 @@ export interface CmsBackend {
   auth_endpoint?: string;
   cms_label_prefix?: string;
   squash_merges?: boolean;
+  signoff_commits?: boolean;
   proxy_url?: string;
   commit_messages?: {
     create?: string;