Replace #28849. Thanks to @yp05327 for the looking into the problem.
Fix#28840
The old behavior of newSignatureFromCommitline is not right. The new
parseSignatureFromCommitLine:
1. never fails
2. only accept one format (if there is any other, it could be easily added)
And add some tests.
(cherry picked from commit a24e1da7e9e38fc5f5c84c083d122c0cc3da4b74)