Re: Quick command to count commits

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, 6 Jan 2009, Henk wrote:
>
> For GitExtensions (windows git ui) I need a command to count all commits. I
> now use this command:
> git.cmd rev-list --all --abbrev-commit | wc -l
> 
> This works perfect but its very slow in big repositories. Is there a faster
> way to count the commits?

Nope. Possibly drop the --abbrev-commit part, but it's not going to hurt 
_that_ much, and maybe avoiding piping the data can be a win in some 
cases.

Basically, to get commit counts, you need to traverse the whole history, 
or at least cache it. So the only way to speed things up is

 - make sure your repository is well-packed. That will speed things up by 
   an absolutely huge amount, if they weren't well-packed before. Just a 
   single large pack-file, not lots of small packs, and not lots of loose 
   objects.

 - you can certainly cache it. Just index by the sha1sum of all the heads, 
   and you have a great cache. Just keep a single entry. So _if_ the 
   repository seldom changes, and you do this a lot, you'll at least only 
   pay the price once.

IOW, do something like this:

	#!/bin/sh
	revs=$(git rev-parse --all)
	index=$(echo "$revs" | sha1sum | cut -d' ' -f1)
	cached=$(cat .git/commit_nr_cache)
	cached_index=$(echo "$cached" | cut -d' ' -f1)
	if [ "$index" == "$cached_index" ]; then
		echo "$cached" | cut -d' ' -f2
		exit
	fi
	nr=$(git rev-list $revs | wc -l)
	echo "$index $nr" > .git/commit_nr_cache
	echo $nr

and you now have a stupid single-entry cache.

Totally untested. You'll need to do _some_ work yourself ;)

		Linus