Version control systems

Go here for how I'm using Subversion to manage the process pieces

For this project I am using 2 version control systems:

• Subversion will be used for maintaining the source code repositories.
• git will be used for monitoring various directories for changes

Git vs Subversion

(About a month into the project). I can now say that I've tried git for managing my scripts, html, php, etc. My observations..

1. Git generates change sets, which are changes to sets of files. There really is no file version identifier. It lends itself to making many changes across a large set of files, stabilizing those changes then releasing the stabilized set as the next revision.
2. Git is designed for distributed, multi-author version control. There is no single point of truth except by convention and agreement. The emphasis is on "pulling" the changes you want from any other repository, rather than "pushing" or "committing" them to a central location for safe keeping. There is not much advantage to this if there is just one person doing the development
3. You can make git act in a "svn-ish" fashion, ie, with a central repo, but it is unnatural.

Git for tracking /etc

One of the issues I've run into is that Xen (in particular) likes to scribble in somewhat undocumented places. Git has the quality that a directory with existing content can become a 'sandbox' with just a few commands

cd /etc
echo "*passwd*" > .gitignore
echo "*shadow*" >> .gitignore
echo "*lvm*" >> .gitignore
echo "*cache*" >> .gitignore
echo "*gconf*" >> .gitignore
git init
git add *
git commit -m "Adding all of :/etc"

Once this is done, "git status" quickly shows you what files have changed and a "git diff" will show you how they've changed. I do this for /etc, /var/lib/xen (ignoring images), and /var/lib/libvirtd. At this point I'm not pushing or merging these individual repos together, though I may in the future. It provides a very handy way of tracking what and how things have changed.

As a note, this saved me a lot of work while working on this project. While in the /etc/xen directory I executed "scp tempfile cobbler-lt" which of course blew away cobbler-lt rather than copying the file to the cobbler-lt vm. OUCH!. A quick git diff and I was back in business.

Centralized git

1. Create a normal git repo with content
2. Decide on your central location
   • mkdir /somedir/central
   • cd central
   • git --bare init --shared
   • git --bare fetch /somedir/source_git_repo
   • an 'ls' at this point will show you a set of files that looks like an svn repo directory. This is not a working git tree. You can not make any changes here.
3. cd /somedir
4. git clone /somedir/central local_git
5. cd local_git;touch t;git add t;git commit -m t;git push
6. You can pull from or to local_git as usual.
7. You can push from local_git into central.
8. You can push from any other repo cloned from central or local_git
9. You can not push from your original source_git_repo. Nor can you pull from it into central. Delete it.
10. I never figured out how to push anything other than master. I'm sure it's possible, I just lost interest.