Multiple heads of the same branch using Mercurial

(No progress on the chemical structure tool -- I've been working on my Other Project)

Anyway, today I'd like to tell you about one of our recent problems that we had to overcome using Mercurial. Mostly for reference purposes so I don't forget about the solution, but if you find it useful that's great.

So, we've been using Mercurial for a few months now, and I personally like it a lot. However, that doesn't mean we've been without our share of "learning experiences." Recently we discovered how important it was to pull before pushing changes on a commonly worked on branch (in this case, it's our Test branch).

Since this branch gets merges from our development branches quite often, there's no guarantee that you have the most up-to-date version when you're merging with it. So one of our philosophies is to just always pull before merging anything.

Now what happens when you don't do this? Well, let's look at our scenario:

• Changes are merged into Test and pushed to the remote repository from machine A. Everything's OK 
• Machine B also merges changes into Test but does not see machine A's changes on Test.
• Machine B attempts to push, Mercurial warns that there will be two heads on the Test branch. Otherwise it would have to decide whose changes are the "official" ones, and that's not it's problem. 
• Machine B then pulls and observes multiple heads on the Test branch. 

Oops. Now, back when we were working on a group project for school, we had this problem but I didn't understand it enough to fix it. This time however, we fixed it and now it's just an inconvenience. We pull the changes on machine B so we see the multiple heads, and just merge one head into the other. Problem solved!

And everyone's happy!

Now, I'm sure some of you are thinking "duh, Chris, what's so hard about that?" Sorry guys, I'm still working on a complete understanding of Mercurial. But that's one less step we have to deal with now!