feat: attach git diff in the PR description (#323)

* feat: attach `git diff` in the PR description

Signed-off-by: Junya Sasaki <junya.sasaki@tier4.jp>

* fix: simplify link symbol

Signed-off-by: Junya Sasaki <junya.sasaki@tier4.jp>

* Update create-prs-to-update-vcs-repositories/create_prs_to_update_vcs_repositories.py

Signed-off-by: Junya Sasaki <junya.sasaki@tier4.jp>

Co-authored-by: Yutaka Kondo <yutaka.kondo@youtalk.jp>

* Update create-prs-to-update-vcs-repositories/create_prs_to_update_vcs_repositories.py

Signed-off-by: Junya Sasaki <junya.sasaki@tier4.jp>

Co-authored-by: M. Fatih Cırıt <xmfcx@users.noreply.github.com>

---------

Signed-off-by: Junya Sasaki <junya.sasaki@tier4.jp>
Co-authored-by: Yutaka Kondo <yutaka.kondo@youtalk.jp>
Co-authored-by: M. Fatih Cırıt <xmfcx@users.noreply.github.com>

create-prs-to-update-vcs-repositories/create_prs_to_update_vcs_repositories.py

@@ -353,11 +353,20 @@ def main(args: argparse.Namespace) -> None:
             # Switch back to base branch
             repo.heads[args.base_branch].checkout()
 
+            # Compose a PR body
+            pr_body = f'''## Description
+This PR updates the version of the repository {repo_name} in autoware.repos.
+
+## What's changed
+
+You can see the changes in https://github.com/{repo_name}/compare/{current_version}...{latest_tag}.
+'''
+
             # Create a PR
             github_interface.create_pull_request(
                 repo_name = args.repo_name,
                 title = title,
-                body = f"This PR updates the version of the repository {repo_name} in autoware.repos",
+                body = pr_body,
                 head = branch_name,
                 base = args.base_branch
             )