Basic CVS from Emacs

I've been a long time user of Emacs both on UNIX/Linux and on Windows, and I'm reasonably proficient now I suppose - I have a small set of keyboard short cuts that I use regularly for things like switching between buffers and doing query-replace operations - but I'm aware that I've only scratched the surface of what the program is capable of (after all, I still think it's "just" an editor).

So my most recent discovery is probably not news to a lot of people, but I still think it's pretty neat: specifically, the ability to access CVS version control operations on a file directly from within Emacs using its standard version control interface, vc.el.

A quick summary of the basics: to load vc.el and activate the functions, first do Ctrl-x Ctrl-q, then:

• Use the sequence Ctrl-x v = to see differences between the current buffer and the last CVS version (i.e. cvs diff), and
  
• Use the sequence Ctrl-x v v to commit your changes - this opens a new buffer to write the commit message, and when you're done use Ctrl-c Ctrl-c to finish the commit.

Other operations are available but I think these are the ones that will be most useful to me, as it means I won't need to leave the editor in order to commit changes from the command line. (Also with this method I don't need to "revert" the buffer after CVS has updated any keywords in the file, which I always have to do when using editor-plus-command-line.)

So far I've been using this with GNU Emacs 22.2.1 and CVS 1.12.3 on Ubuntu Linux. I'm guessing that Emacs works out that the file is under version control by detecting the CVS subdirectory, and that the same (or similar) key sequences might also work for SVN - but I have no idea yet if this will work on Windows using Xemacs and TortoiseCVS (I will report back once I've had a chance to investigate further).

Simple distributed version control using Dropbox

Over the last 2 years I've been developing a few personal software projects, and while I'd happily been using CVS for version control on one machine (a laptop running Windows XP), there were two significant friction points: 1) how to transfer code to my other machines (I'm running two other separate operating systems - Ubuntu Linux and Windows XP - on a single dual-booting desktop PC), and then merge any changes or fixes back again, and 2) how to ensure that the CVS repositories were being regularly and reliably backed up.

One of the issues with the first problem is that while it's irritating and error-prone to work around (and has a deterrent effect on performing cross-system testing), it doesn't cause enough real pain to force you to properly deal with it. The second problem is that hardy perennial, that making back ups never really feels that urgent (until immediately after your hard drive fails).

So I had been limping along for a while until a few months ago when I read an article called "Easy Version Control" by Ryan Taylor (havocinspired.co.uk) in August's .net magazine. Ryan's article covers a lot of other things, but for me the key suggestion is to use the free Dropbox file synchronisation service (which also provides you with up to 2GB of online storage) to back up and share the version control repositories.

The actual set up process is simple:

1. Install the Dropbox client on the first machine,
2. Put your repositories inside the special Dropbox directory/folder that is created when the client is installed,
3. Install Dropbox clients on each of the other machines where you want to access the repositories.

The Dropbox clients do the rest: they automatically synchronise the Dropbox directories/folders - including the repositories - across all machines. You can then check out working copies of your code and commit changes back to the repository on any machine, which will be automatically reflected on all the others. Additionally, a synchronised copy of the repository is also held on the Dropbox servers (thus taking care of the back up issue).

In Ryan's article he works with SVN rather than CVS but this doesn't appear to be a problem - neither does sharing repositories between Linux and Windows (where I'm using TortoiseCVS ). (He also suggests that several people could work with the same repository at once by enabling sharing in Dropbox for the appropriate directories/folders.) So all in all this seems like an ideal solution for simple distributed version control for personal projects like mine.