Local shallow git cloning with hard-links
clone, git
Solution
It appears that it is impossible to do local shallow cloning with hard links among object databases, at least as of git 1.7.12. `git clone --depth 1 --single-branch` explicitly warns that `--depth` is ignored in local clones, and to use `file://`. So you will need to choose between hard links and shallow cloning.
The hard links do work even when repository changes, at least for a time, because git adds new objects to new files, and never modifies existing files. However, it does occasionally repack the object database for efficiency, and I don't see how the hard links could be preserved then.
If you choose shallow cloning, you can create the clone with `git clone --single-branch --depth 1 file://old_repo_dir` options. I find it annoying that `--depth 1` means 1 item of history, so you'll get not only the latest commit, but also its parent (or parents if it's a merge). The parent gets the commit message from the original repository, but the commit message lies because the commit in actuality contains the creation of the entire tree.
I prefer to start off with a single commit with a commit message of my choosing that creates the initial tree. This is obtained by first creating a new branch without history in the old repo, and then pulling that branch into the new empty repo. I tested this on a huge repo with a 664MB object database with 673k objects (the Emacs bzr repository converted to git). When the new repo received the pull, it had a 36MB object database with 3477 objects — so the excess content was apparently pruned. Here are the exact steps:
# at the old repo:
git checkout --orphan tmp-snapshot
git commit -m "Initial commit."
# at the new repo location:
git init
git pull OLD_REPO_DIR tmp-snapshot:master
# back at the old repo:
git branch -D tmp-snapshot # no longer serves a purpose
Now the `master` branch of the new repo contains a single commit with a tree identical to the tree of the old repo, and without any history.
Problem
On my local filesystem, I want to be able to only clone the head of git repo (A) so no history comes along to a new git repo (B). But I want the benefits of hard-links for the files now in B to save on space. Is there a way to do this? Do the hard-links even help once repo A changes? Thanks!