Why is it impossible to change your username in SourceTree?

[Nick Myers]

I entered the wrong username when trying to do a Pull.  Every time I try to do a Pull, it prompts me for a password, but never for a username.  I've looked at dozens of posts online, and clicked through every menu I could find, and I've concluded that it is impossible to change your username.  Why???

[cvcolomb]

Same, or at least similar problem here. One of my repos has a different username, but Sourcetree is only showing me the default. I go into setting for that repository and change username, but it isn't used when I try to pull. I tried editing the config file as well, no change.

[Alan Hayes]

Hi, I also am completely frozen out of Source Tree 2.2 on my Macbook. 

I installed SourceTree, entered an incorrect username, and now I can't change it.

Also, Preferences are disabled, clicking anything just makes a bell sound.

I've tried uninstalling, and there are no remnant config files that I can find. But after reinstalling, I still see my incorrect username, which I cannot change.

Help!

Alan