Framework: Update detect-mpi-comm-world GitHub action (#12199)

* Framework: Fix issue with detect-mpi-comm-world.yml when base branch is out of sync with origin/develop

* Framework: Remove check for uncommited changes from the check-mpi-comm-world-usage script, as it may provide incorrect output

commonTools/test/utilities/check-mpi-comm-world-usage.py

@@ -53,7 +53,6 @@ def parse_diff_output(changed_files):
                 line_counter = 0
                 for line in lines:
                     if line.startswith("+"):
-                        line_counter += 1
                         if (
                             "MPI_COMM_WORLD" in line
                             and not "CHECK: ALLOW MPI_COMM_WORLD" in line
@@ -62,23 +61,30 @@ def parse_diff_output(changed_files):
                             # and "CHECK: ALLOW MPI_COMM_WORLD" is not present
                             changed_lines.append(start_line + line_counter)
 
+                        line_counter += 1
+
             if changed_lines:
                 files[file_name] = changed_lines
 
     return files
 
 
-def get_changed_files_uncommitted():
-    """Get a dictionary of files and their changed lines where MPI_COMM_WORLD was added from uncommitted changes."""
-    cmd = ["git", "diff", "-U0", "--ignore-all-space", "HEAD"]
-    result = subprocess.check_output(cmd).decode("utf-8")
-
-    return parse_diff_output(result)
+def get_common_ancestor(target_branch, feature_branch):
+    cmd = ["git", "merge-base", target_branch, feature_branch]
+    return subprocess.check_output(cmd).decode("utf-8").strip()
 
 
-def get_changed_files(start_commit, end_commit):
-    """Get a dictionary of files and their changed lines between two commits where MPI_COMM_WORLD was added."""
-    cmd = ["git", "diff", "-U0", "--ignore-all-space", start_commit, end_commit]
+def get_changed_files(target_branch, feature_branch):
+    """Get a dictionary of files and their changed lines between the common ancestor and feature_branch."""
+    start_commit = get_common_ancestor(target_branch, feature_branch)
+    cmd = [
+        "git",
+        "diff",
+        "-U0",
+        "--ignore-all-space",
+        start_commit,
+        feature_branch
+    ]
     result = subprocess.check_output(cmd).decode("utf-8")
 
     return parse_diff_output(result)
@@ -109,21 +115,12 @@ def print_occurences(changed_files, title):
     end_commit = parser.parse_args().head
     print(f"End commit: {end_commit}")
 
-    commited_occurences = get_changed_files(start_commit, end_commit)
-    uncommited_occurences = get_changed_files_uncommitted()
-
-    mpi_comm_world_detected = commited_occurences or uncommited_occurences
+    mpi_comm_world_detected = get_changed_files(start_commit, end_commit)
 
     if mpi_comm_world_detected:
-        if commited_occurences:
-            print_occurences(
-                commited_occurences, "Detected MPI_COMM_WORLD in the following files:"
-            )
-        if uncommited_occurences:
-            print_occurences(
-                uncommited_occurences,
-                "Detected MPI_COMM_WORLD in the following files (uncommited changes):",
-            )
+        print_occurences(
+            mpi_comm_world_detected, "Detected MPI_COMM_WORLD in the following files:"
+        )
 
         sys.exit(1)  # Exit with an error code to fail the GitHub Action
     else: