Make CheckForCommitObjects check gitlinks and .gitmodules

issues.skia.org/issues/324072603: DEPS were renamed but the
corresponding gitlinks and gitmodules entry were not updated. Update
to check that

1. DEPS entries point to gitlinks (if SYNC)
2. .gitmodules entries match paths of gitlinks

Bug: 324118800
Change-Id: I4c97b54c1912712aef309584bebaa4ea3b24d5df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5273762
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Gavin Mak <gavinmak@google.com>

presubmit_canned_checks.py

@@ -1999,6 +1999,11 @@ def CheckForCommitObjects(input_api, output_api):
     for commit_tree_entry in commit_tree_entries:
         git_submodules[commit_tree_entry[2]] = commit_tree_entry[3]
 
+    gitmodules_file = input_api.os_path.join(input_api.PresubmitLocalPath(),
+                                             '.gitmodules')
+    with open(gitmodules_file) as f:
+        gitmodules_content = f.read()
+
     mismatch_entries = []
     deps_msg = ""
     for dep_path, dep in deps['deps'].items():
@@ -2019,7 +2024,23 @@ def CheckForCommitObjects(input_api, output_api):
             continue
 
         if commit_hash in git_submodules:
-            git_submodules.pop(commit_hash)
+            submodule_path = git_submodules.pop(commit_hash)
+            if not dep_path.endswith(submodule_path):
+                # DEPS entry path doesn't point to a gitlink.
+                return [
+                    output_api.PresubmitError(
+                        f'Unexpected DEPS entry {dep_path}.\n'
+                        f'Expected path to end with {submodule_path}.\n'
+                        'Make sure DEPS paths match those in .gitmodules \n'
+                        f'and a gitlink exists at {dep_path}.')
+                ]
+            if f'path = {submodule_path}' not in gitmodules_content:
+                return [
+                    output_api.PresubmitError(
+                        f'No submodule with path {submodule_path} in '
+                        '.gitmodules.\nMake sure entries in .gitmodules match '
+                        'gitlink locations in the tree.')
+                ]
         else:
             mismatch_entries.append(dep_path)
             deps_msg += f"\n [DEPS]      {dep_path} -> {commit_hash}"