Blocked everytime we select "Working directory changes" for a big repo.

[srazi]

Steps to reproduce: 1- I opened qt-creator repo. (> 55K commits): 2- After it loaded completely memory usage is: 3,009,720 KB 3- Select a commit. 4- Memory usage changes to: 2,165,040 KB 5- Again, select Working directory changes 6- After ~5s it start to do something and memory usage changed to: 3,005,344

So it seems it re-computes working directory changes everytime we select Working directory changes.