Update format-diff script to add text to new files (facebook#14143)

Summary:
Fixing internal validator failure

```
Every project specific source file must contain a doc block with an appropriate copyright header. Unrelated files must be listed as exceptions in the Copyright Headers Exceptions page in the repo dashboard.
A copyright header clearly indicates that the code is owned by Meta. Every open source file must start with a comment containing "Meta Platforms, Inc. and affiliates"
https://github.com/facebook/rocksdb/blob/main/buckifier/targets_cfg.py:
The first 16 lines of 'buckifier/targets_cfg.py' do not contain the patterns:
	(Meta Platforms, Inc. and affiliates)|(Facebook, Inc(\.|,)? and its affiliates)|([0-9]{4}-present(\.|,)? Facebook)|([0-9]{4}(\.|,)? Facebook)
```

While fixing the text to pass the linter, I took the opportunity to modify `format-diff.sh` script to add the copyright header automatically if missing in new files.

Pull Request resolved: facebook#14143

Test Plan:
```
$> make format
```
**new python file**
```
build_tools/format-diff.sh
Checking format of uncommitted changes...
Checking for copyright headers in new files...
Added copyright header to build_tools/test.py
Copyright headers were added to new files.
Nothing needs to be reformatted!
```
**new header file**
```
build_tools/format-diff.sh
Checking format of uncommitted changes...
Checking for copyright headers in new files...
Added copyright header to db/db_impl/db_impl_jewoongh.h
Copyright headers were added to new files.
Nothing needs to be reformatted!
```

Reviewed By: hx235

Differential Revision: D87653124

Pulled By: jaykorean

fbshipit-source-id: 164322cfcd2c162bb3b41bb8f3bafefa3f20b695

Author: jaykorean

buckifier/targets_cfg.py

@@ -1,4 +1,6 @@
-# Copyright (c) Meta Platforms, Inc. and its affiliates. All Rights Reserved.
+#  Copyright (c) Meta Platforms, Inc. and affiliates.
+#  This source code is licensed under both the GPLv2 (found in the COPYING file in the root directory)
+#  and the Apache 2.0 License (found in the LICENSE.Apache file in the root directory).
 
 rocksdb_target_header_template = """# This file \100generated by:
 #$ python3 buckifier/buckify_rocksdb.py{extra_argv}

build_tools/format-diff.sh

@@ -148,6 +148,70 @@ else
   echo "Checking format of uncommitted changes..."
 fi
 
+# Check for missing copyright in new files
+echo "Checking for copyright headers in new files..."
+
+# Get list of new files (added, not just modified)
+if [ -z "$uncommitted_code" ]; then
+  # Post-commit: check files added since merge base
+  new_files=$(git diff --name-only --diff-filter=A "$FORMAT_UPSTREAM_MERGE_BASE" -- '*.h' '*.cc' '*.py' $EXCLUDE)
+else
+  # Pre-commit: check staged new files
+  new_files=$(git diff --name-only --diff-filter=A --cached HEAD -- '*.h' '*.cc' '*.py' $EXCLUDE)
+fi
+
+if [ -n "$new_files" ]; then
+  files_missing_copyright=""
+
+  for file in $new_files; do
+    if [ -f "$file" ]; then
+      # Check if file is missing copyright
+      # For .py files, check for Python-style comment
+      # For .h and .cc files, check for C++-style comment
+      if [[ "$file" == *.py ]]; then
+        if ! grep -q "Copyright (c) Meta Platforms, Inc. and affiliates" "$file"; then
+          files_missing_copyright="$files_missing_copyright $file"
+          # Add copyright header to Python file
+          temp_file=$(mktemp)
+          {
+            echo "#  Copyright (c) Meta Platforms, Inc. and affiliates."
+            echo "#  This source code is licensed under both the GPLv2 (found in the COPYING file in the root directory)"
+            echo "#  and the Apache 2.0 License (found in the LICENSE.Apache file in the root directory)."
+            echo
+            cat "$file"
+          } > "$temp_file"
+          mv "$temp_file" "$file"
+          echo "Added copyright header to $file"
+        fi
+      elif [[ "$file" == *.h ]] || [[ "$file" == *.cc ]]; then
+        if ! grep -q "Copyright (c) Meta Platforms, Inc. and affiliates" "$file"; then
+          files_missing_copyright="$files_missing_copyright $file"
+          # Add copyright header to C++ file
+          temp_file=$(mktemp)
+          {
+            echo "//  Copyright (c) Meta Platforms, Inc. and affiliates. "
+            echo "//  This source code is licensed under both the GPLv2 (found in the "
+            echo "//  COPYING file in the root directory) and Apache 2.0 License "
+            echo "//  (found in the LICENSE.Apache file in the root directory)."
+            echo
+            cat "$file"
+          } > "$temp_file"
+          mv "$temp_file" "$file"
+          echo "Added copyright header to $file"
+        fi
+      fi
+    fi
+  done
+
+  if [ -n "$files_missing_copyright" ]; then
+    echo "Copyright headers were added to new files."
+  else
+    echo "All new files have copyright headers."
+  fi
+else
+  echo "No new files to check for copyright headers."
+fi
+
 if [ -z "$diffs" ]
 then
   echo "Nothing needs to be reformatted!"