gcc-changelog: Add warning for auto-added files
git_email.py prints now a warning for files added automatically.
git_check_commit.py does likewise but only with --verbose.
It prints one line per ChangeLog file, either stating the file
or if more than one the number of files.
contrib/ChangeLog:
* gcc-changelog/git_check_commit.py (__main__): With -v print a
warning for the auto-added files.
* gcc-changelog/git_commit.py (GitCommit.__init__): Add self.warnings.
(GitCommit.check_mentioned_files): Add warning for auto-added files.
(GitCommit.print_warnings): New function.
* gcc-changelog/git_email.py (__main__): Remove bogus argument to
GitEmail constructor; print auto-added-files warning.
* gcc-changelog/test_email.py (test_auto_add_file_1,
test_auto_add_file_2): New tests.
* gcc-changelog/test_patches.txt: Add two test cases.