Tito fails to get a commit count when there is more than one root commit

[adamladd17]

get_commit_count in common always returns 0 if there is more than one root commit (this scenario pops up when you merge two old repositories into one new one).

I was able to fix this by adding output= output.split("\n")[-1] under line 919 in method get_commit_count of common.py

This just takes the initial root commit in case there are multiple.