On Tue, 19 Sep 2006, Petr Baudis wrote:
Dear diary, on Tue, Sep 19, 2006 at 11:07:45PM CEST, I got a letter
where Joel Dice <dicej@xxxxxxxxxxxxx> said that...
Implementation:
A simple, efficient implementation of this feature would be based on a
single file, $GIT_DIR/history, which would contain a newline-delimited
list of SHA commit IDs in chronological order, oldest first. The current
repository IRN would be calculated as the size of that file divided by the
SHA+newline length, and the commit ID of any IRN could be determined by
seeking to the correct offset in that file. Every commit would cause a
new line to be appended to the history file with that commit's ID.
Finally, a history file could be generated for an existing repository by
serializing the commit history based on chronological order.
We already have support for recording something similar, it's called a
revlog. You would just need to modify it to aggregate all the branches
in a single file.
Thanks - I'll look at that.
Also, multiple IRNs could refer to a single real commit if you do e.g.
cg-admin-uncommit, since revlog logs revision updates, not new revisions
created. This may or may not be considered a good thing. If you rather
want to just create a new IRN at commit object creation time, also note
that some tools _might_ validly create commit objects and then throw
them away, which would generate non-sensical (and after prune, invalid)
IRNs.
I'm not too worried about cg-admin-uncommit or git-reset, since the IRN
feature is intended mainly for shared repositories. I would suggest that
such commands simply be disallowed for such repositories.
The problem of temporary commits certainly needs to be addressed. In this
case, may I assume nothing under $GIT_DIR/refs is ever modified? If so,
perhaps I could somehow hook into the git-update-ref step. Is that what
the revlog code does?
- Joel
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