I don't know how successful of a metaphor this would be for students, but for developers who haven't had any familiarity with DVCS that I have worked with, I us

I don't know how successful of a metaphor this would be for students, but for developers who haven't had any familiarity with DVCS that I have worked with, I use a coat-rail analogy with some success: You start with a "main" rail of coats. Each coat is given a number, indicating what order it is in. You start adding coats to a new, empty, rail, using the next number. When you are done collecting coats on this new rail, you want to move your coats onto the original rail. In the time it has taken you to collect the coats onto your rail, someone else has already added coats from their new rail to the end of the "main" rail, and they used the same base number that you have - which means you cannot just add the coats from your rail onto the main rail, else the numbering would be broken - we call this a conflict. (NB: There is a magic guardian of the rails that means this just cannot happen, which is a plot device that is just to make this metaphor work so don't question it, it's just a metaphor.) To resolve the conflict you have the following "rebase" options: - Slide all of the coats on the main rail up to make room for yours, and update all of the numbers on your coats, using the new number from the last coat as the base number for your rail's sequence. This ensures that everything on the main rail is "before" your rail. This is the equivalent of a rebase. After this, you can then put your coats on the end of the main rail without conflict. - Then there is the option to take a copy of the main rail onto the front of your rail, and organising the coats one-by-one (much like in the above), placing your coat(s) in between some of the new coats on the main rail, then forcibly replacing the main rail with your updated rail. This last one is just as drastic in reality as it sounds in this metaphor. We call this the "interactive rebase" and it is rewriting history for anyone who has used the main rail before. - Finally we have a merge which means adding one big magic coat at the end that takes the coats from both rails and combines them in a singularity, with the new base number being Hawking's radiation or something, I dunno. The metaphor is no good for merges. (Truth be told: the entire metaphor started in my head some years ago with just the visualisation of that distinct coat rail sweep noise to squish the garments on the rail to onside to fit what our main protagonist is holding onto the rail, the rest I just back-filled over time)