Performance problem with the diff processor

[WalkingDexter]

I noticed that on a large project with a large number of files, the diff processor is much slower than the staged processor even if no changes were made to the codebase. After a short investigation I found that the problem is related to getUntrackedFileList - it's always refreshed inside getPreProcessor. If I remove the refreshing in getPreProcessor the diff processor works fast.

[WalkingDexter]

The problem is present in versions 2.0.3 and 2.0.2. Everything is OK when I downgrade to 2.0.1. Most likely the problem is related to this change #27.

[vippelinalf]

I can also confirm this issue, extremely slow in our pretty big codebase. Downgrading to 2.0.1 made it way much faster. Can we simply remove the refreshing in getPreProcessor? I guess its there for a reason :)