speed issues with large commit in tree view

[pgundlach]

I have a medium sized project and imported all the files into git ("initial import"). When gitx (L) 082 tries to display this commit, gitx freezes for a while. I liked the behavior of the original gitx where you have to press a special key to open the big commit.

[glyn]

gitx (L) is much slower than the original gitx even on small commits. It seems to take ages just loading the 600+ commits in the repo. and the UI becomes unresponsive during this action, like it's running the UI and the scanning on a single thread.

[glyn]

This repo shows the problem if that's useful: https://github.com/eclipse/virgo.kernel.git or, equivalently, git://git.eclipse.org/gitroot/virgo/org.eclipse.virgo.kernel.git

[idris]

This might be related to #129