No, that's a lot of work :) But if you want to see all commits that are in branch 1.8 that are not in branch 1.7.4 you can run this command:
git log v1.7.4..1.8
I guess you just checked up to when the 1.7.4 merged into 1.8 for the last time that's why you lost so many commits. In fact, this is the first commit in the 1.8 branch (look at the year!):
Author: pupi1985 <email@example.com>
Date: Wed Dec 3 08:14:36 2014 -0300
Added qa_format_number function to replace all number_format
BTW, I don't really know what will happen with commits in dev since v1.7.4. I mean, will they be part of v1.7.5 or 1.8? If they will be part of 1.8, then there are more commits to look at. Otherwise, you can disregard them.