Junio C Hamano <junkio@xxxxxxx> writes:
> Here are the topics that have been cooking.
> * sb/fetch (Mon Mar 12 19:01:11 2007 -0700) 19 commits
> + git-fetch.sh:append_fetch_head() no longer has a remote_nick
> argument
> + git-fetch: Split fetch and merge logic
>
> I have a soft spot to anything that claims to be a clean-up, but
> I suspect that the shell loop this series introduces may defeat
> the git-fetch--tool optimization. Also I think having to base
> the patch on this made Paolo's "dot is special token to mean
> 'git pull' merges from a local branch" needlessly complex (but I
> haven't tried rewriting it myself without these two). Although
> I merged these to 'next', I am considering to revert them.
I tried the "NULL fetch between 1000-refs repositories" test,
which prompted the git-fetch--tool work that was done on
jc/fetch topic in 'next', with the following versions:
(1) 1.5.0 (without any git-fetch--tool optimization)
(2) master (ditto)
(3) master with jc/fetch (but not sb/fetch topic)
(4) next ((3) plus sb/fetch and others)
The test scripts are at the end of this message. Both (1) and
(2) take 3 minutes 7 seconds wallclock time. (3) improves it
down to 15 seconds. (4) makes the operation spend 24 seconds
(the times are all on my primary machine x86-64 with 1GB, hot
cache and average of three runs each).
So the "Split fetch and merge" series hurts the performance
quite a bit. If it had enough "code clean-up" merit to warrant
this, I would say it probably is a cost we should bear, but I
personally do not see it.
Paolo recently worked on top of next to base the fake '.' remote
patch. This wants to allow:
[branch "foo"]
remote = .
merge = refs/heads/master
with an implicit (meaning, you do not have to have this in your
configuration):
[remote "."]
url = .
fetch = refs/*
so that you can say:
$ git checkout foo
$ git pull
to merge from the local 'master' branch.
I haven't reimplemented Paolo's patch on top of (3) above for
comparison, but I have a feeling that it would not have been
helped by the alleged clean-up value of "Split fetch and merge"
patch (iow, I do not think it would be the case that the code
got clearer to understand thanks to the clean-up).
What Paolo's patch needs to do is to bypass the actual fetch and
generate the following line in .git/FETCH_HEAD:
sha1-of-our-master <TAB> <TAB> branch 'master' of .
I even suspect that "Split fetch and merge", by introducing
FETCH_FETCHED and making FETCH_HEAD generated from it, made
Paolo's patch more difficult to do and the end result less
efficient.
So unless there is a convincing counterexample otherwise, I'd
like to revert the "Split fetch and merge" series.
-- >8 -- setting up test repositories -- >8 --
#!/bin/sh
rm -fr origin clone
mkdir origin
cd origin
git init
: >hello
git add hello
git commit -a -m 'initial'
i=0
while test $i -lt 500
do
git tag t$i
git branch b$i
i=$(($i+1))
done
: >bye
git add bye
git commit -a -m 'second'
while test $i -lt 1000
do
git tag t$i
git branch b$i
i=$(($i+1))
done
cd ..
-- >8 -- NULL fetch test -- >8 --
#!/bin/sh
cd clone
echo '* fetching'
time git fetch origin
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