Re: git filter-branch should run git gc --auto

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> Kevin Ballard <kevin@sb.org> writes:
>
>> I just glanced at git-filter-branch.sh (and I must say I was
>> incredibly surprised to find out it was a shell script) and it seems
>> it never runs git-gc or git-repack. Doesn't that end up with the same
>> problems as git-svn sans git-repack when filtering a large number of
>> commits? I was just thinking, if I were to git-filter-branch on my
>> massive repo (in fact, the same repo that started this thread, with
>> over 33000 commits in the upstream svn repo), even if I just do
>> something as simple as change the commit msg wont I end up with
>> thousands of unreachable objects? I shudder to think how many
>> unreachable objects I would have if I pruned the entire dports
>> directory off of the tree.

Another thing I forgot to say in my previous message.  The old
refs are kept in reflogs and also in refs/original/, so you will
not be creating new unreachables even if you rewrite many objects.

>> Am I missing something, or does git-filter-branch really not do any
>> garbage collection? I tried reading the source, but complex bash
>> scripts are almost as bad as perl in terms of readability.
>
> Theoretically yes, and it largely depends on what you do, but
> filter-branch goes over the objects that already exists in your
> repository, and hopefully you won't be rewriting majority of
> them.
>
> So the impact of not repacking is probably much less painful in
> practice.
>
> But again as I said, it largely depends on what you do in your
> filter.  If you are upcasing (or convert to NFD ;-)) the
> contents of all of your blob objects, you would certainly want
> to repack every once in a while.

Something like this, perhaps?

 git-filter-branch.sh |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index ebf05ca..8e44001 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -299,6 +299,12 @@ while read commit parents; do
 			die "msg filter failed: $filter_msg"
 	sh -c "$filter_commit" "git commit-tree" \
 		$(git write-tree) $parentstr < ../message > ../map/$commit
+
+	if test $(( $i % 512 )) = 0
+	then
+		git gc --auto
+	fi
+
 done <../revs
 
 # In case of a subdirectory filter, it is possible that a specified head