Use a data factory for commit properties and reduce code duplication.
* bzrlib/tests/test_log.py: (TestLogMixin.wt_commit): Helper acting as a data factory for commit properties. (TestCaseForLogFormatter): Use TestLogMixin and wt_commit() (TestCaseForLogFormatter.assertFormatterResult): Get rid of normalize_log() use. (TestCaseForLogFormatter, TestShortLogFormatterWithMergeRevisions, TestLongLogFormatter, TestLineLogFormatter, TestGetViewRevisions, TestHistoryChange, TestLogWithBugs): Use wt_commit() and stop using run_bzr().
* bzrlib/tests/blackbox/test_log.py: (TestLog): Use test_log.TestLogMixin and get rid of commit_options(). (TestLogMerges.make_branches_with_merges, TestLogDiff.make_branch_with_diffs): Use wt_commit().