Adds --first-parent options to remove previously deleted files

[andyquinterom]

This causes only merge commits to show which fixed the error. This however, could be added as an extra cli option.

[acaudwell]

Looks promising.

[acaudwell]

Thanks for looking into the issue. This might fix the problem in some cases, but from what I can tell --first-parent causes only the last commit of a merge branch to get included, so it would omit other changes from that branch being shown in Gource. E.g. if an earlier commit on the merge branch added a new file, that event will get discarded.

[Liz4v]

I have just tested it and while I agree that squashing the branches is a problem, I still see it as an improvement over current behaviour.