Malformed signed_data from Commit#extract_signature

I've been seeing weird behavior with Commit.extract_signature where I'm getting some garbage data at the end of the signed data string.

For example:

repo = Rugged::Repository.new('/tmp/test')
commit = '7cd86ea426f277276367bd955f312fcbadd7bc5d'

# Note: I can only reproduce the error if rev_parse is called first
repo.rev_parse(commit)
p Rugged::Commit.extract_signature(repo, commit)

As a result the signed_data portion of the returned array sometimes has a \n as the last character. However, I get seemingly random data in that last byte.

I was not able to reproduce this in the tests, however, I can reliably reproduce it if I create new repo locally, add a few signed commits, and then try to extract the signatures via rugged.