How to fix Spotlight not showing apps

I use Apples Spotlight all the time. The shortcut CMD + Spacebar is so convenient that I use it exclusively to open apps, do currency conversion or simple calculations. Recently, though, Xcode disappeared from the Spotlight search. Actually at the moment it happens...

Purging a sensitive file from a Git repository

Well it happens to me all the time. While developing, I add a config file with some sensitive data somewhere in my repository, forget to add it to my .gitignore and accidentally commit it. Then, after another 5 commits, I notice my flaw and then have to somehow purge...