Re: Clone a repository with only the objects needed for a single tag

Ben Lau <benlau@ust.hk> writes:

Depends on what you want to do in that shallow copy.

If the only thing you would want to do is to build it, then you could 'git-tar-tree v2.6.14' and extract that on your notebook. The output is just a tar so there will no history, though.

If you want to develop while on the road, but do not particularly need to be able to inspect the history beyond the point you started, you could create a deliberately broken repository, using the git-shallow-clone script (attached), like this:

    $ git clone -n $mothership satellite
    $ cd satellite
    $ git-shallow-pack --all
    $ rm -f .git/objects/pack/pack-*
    $ mv pack-* .git/objects/pack/.

If the original repository you are cloning from is local, you could instead do:

    $ git clone -l -s -n $mothership satellite
    $ cd satellite
    $ git-shallow-pack --all
    $ rm .git/objects/info/alternates
    $ mv pack-* .git/objects/pack/.

You could develop in this repository, even build up your own commit chains, and when you come back you could push from this repository back to your 'mothership' repository. In essense, any operation that does not require you to have full history should work.

One important thing that would not always work would be to pull into this repository over git-aware protocols, although pulling from your 'mothership' repository would probably work most of the time.

One case that would probably break is if the mothership side reverted a commit beyond this shallow-pack boundary and then you try to pull from there. After the revert, the trees and blobs in that new commit you will be pulling from the mothership are likely to be the same as the ones contained in commits before the shallow clone is made. Because your satellite repo would claim to have everything that is reachable from the tip (as of the time the clone was made) of the branch, you cannot complain if the mothership side assumes you must have those blobs and trees and did not send them to you when you pull.

--- #!/bin/sh # git-shallow-pack

git-rev-parse --revs-only --no-flags --default HEAD "$@" |
while read sha1
do
	echo "$sha1"
	while type=`git-cat-file -t "$sha1"` &&
	      case "$type" in tag) ;; *) break ;; esac
	do
		next=`git-cat-file tag "$sha1" |
			sed -ne 's/^object //p' -e q`
		echo "$next"
		sha1="$next"
	done
	git-rev-parse --verify "$sha1^{tree}" 2>/dev/null &&
	git-ls-tree -r "$sha1" | sed -e 's/^[0-7]* [^ ]* //'
done |
sort -k 1,1 -u |
git-pack-objects pack