git: Introduce .gitmessage

Why:

- Helps ensure consistency in commit messages
- Helps provide more informative commit messages
- Higher likelihood that commit messages conform to https://www.mediawiki.org/wiki/Gerrit/Commit_message_guidelines

What:

- Introduce .gitmessage template file

Bug: T337179
Change-Id: I5126ed398db56e5a3630ff9e74b6f46022c3b1b2

.gitmessage

@@ -0,0 +1,33 @@
+component: Some awesome subject
+
+Why:
+
+- …
+
+What:
+
+- …
+
+Bug: TXXXXX
+#
+# When in doubt, consult https://www.mediawiki.org/wiki/Gerrit/Commit_message_guidelines
+#
+# - Subject should be 50 characters or less
+# - Separate body from subject
+# - Use imperative mood, avoid passive voice
+# - Wrap the body text at 72 chars
+#
+# Explain "why" and "what". If it does not make sense to include
+# this in your commit message, then delete those sections.
+#
+# Don't forget the Bug: line
+# Don't leave a blank line after the Bug: line
+#
+# If you are unsure about what to use for component:
+#  - "HookContainer" could work for changes to include/HookContainer
+#  - "phpunit" for changes to PHPUnit tests
+#  - "Authentication" for changes affecting multiple sections
+#     relating to user authentication
+#
+# Hint: you can enable this to be used as a template for git commit
+# git config commit.template .gitmessage

RELEASE-NOTES-1.41

@@ -52,6 +52,8 @@ For notes on 1.40.x and older releases, see HISTORY.
 * Added ForeignResourcesDir extension.json / skin.json attribute, which should
   point to the directory holding your foreign-resources.yaml file. See
   https://www.mediawiki.org/wiki/Foreign_resources for background.
+* Added a .gitmessage commit template. To use it, run:
+  `git config commit.template .gitmessage`
 * …
 
 === External library changes in 1.41 ===