Had to make a change in an ugly codebase. For this I had to change a config value which was duplicated three times in the code base. So I wanted to refactor the code so that the config was in one place.

I worked on this for two days and it was starting to look good. On the third day when I started to work on this I realized that I couldn't start the server anymore. Looking through version control I figure out that my co-worker had stayed till 3am last night to work on the change I was supposed to make.

I had to spend all morning undoing his commits. Once I was done refactoring the actual change took me ten minutes.

Why the fuck would you stay until the middle of the night to work on someone else's task?!

Could have just asked how it was coming along if I wasn't working fast enough for him.