From an ex CM Consultant (Score 2, Insightful)

Boy this opens a real can of worms for me. Caveat Emptor: I used to be an SCM consultant under the employ of a company formerly known as Continuus software. It is now a part of Telelogic AB. FYI: I am Yet Another Laid Off Person (YALOP).

First. If there's only a dozen of you, and you have a branch, perhaps you should talk. Now if you were like some of my former client base who does follow-the-sun development around the world, this gets a little hairy. By that I mean a company like a TI or BT or Philips is passing code around the world and flexibly allocating resources from multiple sites to a project. Serious commercial SCM systems like Continuus/CM, err.. Telelogic CM/Synergy with DCM and CC with Multisite can be used to coordinate. This is one place that open source has failed to penetrate due to the small size of the potential market and the general antipathy that the average developer has to the CM people. Until, that is, they get religion by losing something very important at a crucial moment ;-) Even then most shops can get by with VSS or PVCS.

OBTW: I'm an ex-developler, system admin, desktop video weenie and computer consultant that backed into SCM. I got religion back around the late 80's but it was pre-emptive. Anyway, concurrent development actually comes in three flavors: concurrent by collision, concurrent by release (patches versus next generation) and finally concurrent by platform (Windows vs Unix, etc). Each is handled differently and under different timeframes (including permanently in the latter).

Your post alludes to the first case of a "popular" file that needs checking out a lot like a header file. In a shop your size, this should be handled by parallel checkout notification (a common feature in commercial high end systems) and hopefully a bit of coordination by phone or shouting over the pod wall. If you are in severe RAD mode, I suggest using a shared work area to enforce sequential checkout. Your SCM tool does build a work area doesn't it? If not, hit yourself on the head and ponder why people like me are now on the dole.

Okay, so you decide to branch anyway since you or the other developer are really going to break things with a rewrite. Hey, wait a minute! Shouldn't a big feature change (or small) be considered as a single unit of work where all of the files changed by the feature get moved through the mill at once. You have just re-invented the wheel known as Change Packages, Task Based CM, ChangeSets and whatever else the marketing wonks are using nowadays. Once again the high end tools have this (or should). Continuus had it back around 1997. Rat got it into CC much more recently, but there it is.

If you have a task based system, it makes life much easier to do merges and to put things in or take things out of the build. Being ex-Continuus, I could pound the pulpit about how build managers can check the configuration and its set of included tasks for consistency, but I won't. Instead I'll just mention that graphic history views and a decent merge tool that takes into account ancestor versions should take care of any merging issues.

One more thing. The sooner you catch the branch and do the merge the better. Don't punt it to CM unless they are ex-developers who know the product as well as or better than you. You may also come to find that an integrated Change Request Management system like ChangeSynergy for Continuus (err Telelogic) and Clearquest for CC become very important in your life.