[ANNOUNCE] chronoversion: chronological archiving script with temporary commits

Hi, I believe that I've now got temporary commits (for bookkeeping, hi-granularity bisecting recent changes) working, so I'm just mentioning there's a new version of chronoversion at

http://www.personal.rdg.ac.uk/~sis05dst/chronoversion.tgz

It maintains two parallel branches, master and temp, using temp for high-granularity temporary commits that can be cleaned away at any time. When a filetree state needs to be recorded on both branches it doesn't merge branches but instead writes a commit tree and then writes commit objects using that tree on both branches. Note: I don't completely understand what all the low-level git stuff is supposed to do so this code was experimented with until it appears to work. Consequently, be very careful about entrusting any hyper-important data to this.

A question for those who understand things: I stash the last written _tree_'s hash in a tag and then when a new "commit's" directory tree is written starts look to see if it's the same SHA value. If it is I know I can avoid the commit. At the moment I'm using

    if os.path.exists(lastTreeFile) and
tree==open(lastTreeFile,"r").read()[:40]:

to be safe just in case a user, eg, goes mad and manually deletes that record. Clearly this is going to hit trouble if git ever decides to put this tag into a packed refs file. Is there any neat way of using builtin stuff like git-rev-parse to ask if a ref has a given SHA1 value and return an easily parsed yes/no answer?

As a side note to Jon Smirl: I think kernel development is relatively special in that you really can't safely test things at the same time as you're editing the code (since clearly a kernel hang/oops/whatever is possible). However, as I work on userspace programs I quite often have my monte-carlo simulation code running on all the cores at the same I edit its source code to try and refine it for the next run. So in general if using git is "free" it'll be because editing tools and git take tiny portions of current CPU's power rather than because there're unused cores :-) (Actually, that's a serious point: I did put in some thought into chronoversion to try and minimise its cpu usage so it intruded as little as possible.)