Re: Re-done kernel archive - real one?

On Mon, 18 Apr 2005, Russell King wrote:

No, that can't work. The pesky tools are helpful, but they really don't do merges worth cr*p right now, excuse my french.

The _real_ way to pull is to do the (horribly complex) thing I described by the merge, but noticing that one of the commits you are merging is a proper subset of the other one, and just updating the head instead of actually doing a real merge (ie skipping the "read-tree -m" and "write-tree" phases).

I'm afraid that until Pasky's tools script this properly, a "pull" really ends up being something like this (which _can_ be scripted, never fear):

NOTE NOTE NOTE! This is untested! I'm writing this within the email editor, so do _not_ do this on a tree that you care about.

	#!/bin/sh
	#
	# use "$1" or something in a real script, this 
	# just hard-codes it.
	#
	merge_repo=master.kernel.org:/pub/linux/kernel/people/torvalds/linux-2.6.git

	echo "Getting object database"
	rsync -avz --ignore-existing $merge_repo/ .git/

	echo "Getting remote head"
	rsync -avz $merge_repo/HEAD .git/MERGE_HEAD

	head=$(cat .git/HEAD)
	merge_head=$(cat .git/MERGE-HEAD)
	common=$(merge-base $head $merge_head)
	if [ -z "$common" ]; then
		echo "Unable to find common commit between" $merge_head $head
		exit 1
	fi

	# Get the trees associated with those commits
	common_tree=tree=$(cat-file commit $common | sed 's/tree //;q')
	head_tree=tree=$(cat-file commit $head | sed 's/tree //;q')
	merge_tree=tree=$(cat-file commit $merge | sed 's/tree //;q')

	if [ "$common" == "$merge_head" ]; then
		echo "Already up-to-date. Yeeah!"
		exit 0
	fi
	if [ "$common" == "$head" ]; then
		echo "Updating from $head to $merge_head."
		echo "Destroying all noncommitted data!"
		echo "Kill me within 3 seconds.."
		sleep 3
		read-tree $merge_tree && checkout-cache -f -a
		echo $merge_head > .git/HEAD
		exit 0
	fi
	echo "Trying to merge $merge_head into $head"
	read-tree -m $common_tree $head_tree $merge_tree
	result_tree=$(write-tree) || exit 1
	result_commit=$(echo "Merge $merge_repo" | commit-tree $result_tree -p $head -p $merge_head)
	echo "Committed merge $result_commit"
	echo $result_commit > .git/HEAD
	read-tree $result_tree && checkout-cache -f -a

The above looks like it might work, but I also warn you: it's not only untested, but it's pretty fragile in that if something breaks, you are probably left with a mess. I _tried_ to do the right thing, but... So it obviously will need testing, tweaking and just general tender loving care.

And if the merge isn't clean, it will exit early thanks to the

	write-tree || exit 1

and now you have to resolve the merge yourself. There are tools to help you do so automatically, but that's really a separate script.

You shouldn't hit the "merge" case at all right now, you should hit the "Updating from $head to $merge_head" thing.

If Pesky wants to take the above script, test it, and see if it works, that would be good. It's definitely a much better "pull" than trying to apply the patches forward..

		Linus