Commit limits
Prevent timeouts when creating/viewing Merge Requests with many commits. Also, reduce the number of commits shown in the UI from 500 to 100.
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14031
This MR avoids Unicorn timeouts in some places and takes 4.5 seconds off load times in others, when manually testing with a 4500-commit compare/MR in the linux repo. It does not limit the number of Commit objects instantiated in memory, just the amount of HTML generated. It seems that having 4500 commits objects is not a problem in itself. If it ever becomes one we could do something for Commit objects like we did for Diff (introduce a CommitCollection or something).