Commits mismatch incorrect error logged

[renatav]

This line contains an error:

taf/taf/updater/updater.py

Line 1152 in fcf131a

additional_commits = new_commits[len(target_commits) :]

This assumes that target repo's commits and commits read from the auth repo have the first commit in common and that target repo's commits just contain additional ones. That is not the case if auth repo was pulled manually and target repo was not

[renatav]

This was reworked as a part of #374
Based on states of repositories, it is determined where the update should start from. So such mismatches should not longer be an issue