If you see every git log entry twice

If you have an unexpectedly long merge time and you see every commit in your git log showing up two times, you or someone else probably changed the history of the repository (such as to remove a big binary file). This changes the commit hash of every commit there is, so when merging these two (actually separate but just happen to have the same code) repositories you'll see them all twice in the history.

This is a warning sign that you should be putting your local copy of the repository aside and cloning a fresh one-- or having other people working on the project do that.