Re: RFC: Design and code of partial clones (now, missing commits and trees OK)

> For those interested in partial clones and/or missing objects in repos,
> I've updated my original partialclone patches to not require an explicit
> list of promises. Fetch/clone still only permits exclusion of blobs, but
> the infrastructure is there for a local repo to support missing trees
> and commits as well.
> ...
> Demo
> ====
>
> Obtain a repository.
>
>     $ make prefix=$HOME/local install
>     $ cd $HOME/tmp
>     $ git clone https://github.com/git/git
>
> Make it advertise the new feature and allow requests for arbitrary blobs.
>
>     $ git -C git config uploadpack.advertiseblobmaxbytes 1
>     $ git -C git config uploadpack.allowanysha1inwant 1
>
> Perform the partial clone and check that it is indeed smaller. Specify
> "file://" in order to test the partial clone mechanism. (If not, Git will
> perform a local clone, which unselectively copies every object.)
>
>     $ git clone --blob-max-bytes=100000 "file://$(pwd)/git" git2
>     $ git clone "file://$(pwd)/git" git3
>     $ du -sh git2 git3
>     116M	git2
>     129M	git3
>
> Observe that the new repo is automatically configured to fetch missing objects
> from the original repo. Subsequent fetches will also be partial.
>
>     $ cat git2/.git/config
>     [core]
>     	repositoryformatversion = 1
>     	filemode = true
>     	bare = false
>     	logallrefupdates = true
>     [remote "origin"]
>     	url = [snip]
>     	fetch = +refs/heads/*:refs/remotes/origin/*
>     	blobmaxbytes = 100000
>     [extensions]
>     	partialclone = origin
>     [branch "master"]
>     	remote = origin
>     	merge = refs/heads/master