Add roll command line to roll CLs

Adds the command line used to generate Chromium -> Dawn rolls to the CL
description of generated CLs. The added lines differ slightly between
manual and autoroll runs since manual runs do not guarantee that test
specs are regenerated.

Bug: 452840620
Change-Id: I13db52c44f87b5acb298355475c2f4984fc98e37
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/280959
Reviewed-by: Jonathan Lee <jonathanjlee@google.com>
Auto-Submit: Brian Sheedy <bsheedy@google.com>
Commit-Queue: Brian Sheedy <bsheedy@google.com>

Author: bsheedy-work

scripts/roll_chromium_deps.py

@@ -35,6 +35,7 @@
 import logging
 import pathlib
 import posixpath
+import shlex
 import subprocess
 import sys
 from typing import Any, Self, Type
@@ -771,6 +772,8 @@ def _generate_commit_message(changed_entries: list[ChangedDepsEntry],
     commit_message_lines.extend(
         _generate_chromium_section(chromium_revision_range, autoroll))
     commit_message_lines.append('')
+    commit_message_lines.extend(_generate_command_section(autoroll))
+    commit_message_lines.append('')
     commit_message_lines.extend(_generate_repo_section(changed_entries))
     commit_message_lines.append('')
     commit_message_lines.extend(_generate_cipd_section(changed_entries))
@@ -810,6 +813,38 @@ def _generate_chromium_section(chromium_revision_range: ChangedRepo,
     return chromium_lines
 
 
+def _generate_command_section(autoroll: bool) -> list[str]:
+    """Generates the commit message section for the script command.
+
+    Args:
+        autoroll: Whether this roll is being done by the autoroller.
+
+    Returns:
+        A list of strings containing lines to append to the commit message.
+    """
+    command_lines = [
+        'DEPS and submodule changes generated by running:',
+    ]
+    script = pathlib.Path(__file__).resolve()
+    script = script.relative_to(DAWN_ROOT)
+    relative_command = [str(script)] + sys.argv[1:]
+    command_lines.append(f'  {shlex.join(relative_command)}')
+
+    test_spec_script = 'infra/specs/generate_test_spec_json.py'
+    if autoroll:
+        command_lines.extend([
+            'Test specs were then regenerated by syncing and running:',
+            f'  {test_spec_script}',
+        ])
+    else:
+        command_lines.extend([
+            'Test specs may have been regenerated by syncing and running:',
+            f'  {test_spec_script}',
+            'This step is manual and may have been missed by the author.'
+        ])
+    return command_lines
+
+
 def _generate_section_for_entry_type(entry_type: Type[ChangedDepsEntry],
                                      changed_entries: list[ChangedDepsEntry],
                                      empty_message: str,