At first glance
DVCS (i.e. Git, BitKeeper, Mercurial, Baazar, etc) main advantage seems related to better branching and merging. Especially for those who experienced the pain of big merge-conflicts of long lived branches (*) with a traditional
VCS (i.e. SVN, Perforce, TFVC, etc).
In reality DVCS born to serve
distributed remote teams.
This is the main point, the distinctive characteristics originate from it and this is why DVCS can do that with simplicity and flexibility.
Here are 2 key distinctive characteristics of DVCS:
- Connection disruptions: when the connection between 2 remote teams goes down, each team member can continue to work autonomously as usual (**) because has the local full copy of the repository including the whole history and everything else that is needed to be autonomous and fully operative locally
- Repository disruptions:
- when a problem affect the central repository: a problem can affect the centralized repository and who can fix the problem is not reachable/available (i.e. because is working in a very different time-zone). Again with DVCS each team member have a self-contained first-class full copy of the repository that make him/her fully operative locally.
- when a remote commit broke the build: a remote team member can commit code with problems (i.e. broke the build, cause merge conflicts, etc) and then go offline, can be not immediately reachable/available (i.e. because is working in a very different time-zone). DVCS enable mechanisms like i.e. the 1-click pull-requests that give a way to deal well with this kind of problems.
A 3dr key distinctive characteristic of DVCS is specifically related to open-source projects:
- Anyone is enabled to and can easily fork a repository to fix a bug or add a feature, and then make a pull-request. This enable and support the spontaneous formations of teams around the open-source project.
All this is explained and expanded in chapters 3 and 14 of the book Continuous Delivery, Addison Wesley.
How are you taking advantage or your DVCS? Are you exploiting the 3 key distinctive characteristics?
Are you exploiting it in other unconventional creative ways?
(*) A root cause for the pain of merging long lived branches is related to the fact that the probability of merge conflict grows faster then linear (polynomially/exponentially depending on the structure of the code-base) with the lifetime of the branch.
Another root cause is that the most difficult merge-conflicts require semantic diff and merging while the main diff and merge tools are text based.
None of these root causes are currently addressed directly by the DVCS.
(**) The impact of a connectivity disruption to Continuous Integration servers and i.e. Tests environments is not automatically resolved by the DVCS. A DVCS enable to easily setup a local autonomous CI environment to continue to work locally until the connectivity is restored.