How git-dedup works
git-dedup maintains one bare SHA-1 Git repository at <store>/pool.git. It fetches branches and tags from each registered remote into separate internal ref namespaces. Git's content hashes deduplicate identical objects across repeated checkouts, forks, and unrelated repositories automatically.
Supported git-dedup clone commands fetch into the pool, then run native git clone --reference <pool> using the real remote as origin. The checkout's objects/info/alternates file points to the pool. Later clones borrow its existing objects. The pool can be on another filesystem.
git-dedup store add imports an existing checkout's refs and HEAD into the pool, installs the alternate, and repacks the checkout to remove private copies of objects already in the pool. It then refreshes the remote when available. Linked worktrees use their shared common object directory. The same process visits discoverable submodules. git-dedup is not a disposable cache: linked checkouts depend on the store for objects.
The pool pins newly seen consumer ref tips during clone, submodule preparation, and checkout adoption, and skips tips that a remote ref in the pool already holds. It records each consumer's Git directory in <store>/consumers. store gc compacts without pruning unreachable objects. Preserving old tips can make the pool grow over time.
store prune is the only command that deletes pool objects. It first re-pins everything each registered checkout can reach: all refs, the HEAD and index of every worktree, reflogs, and in-progress merge, rebase, or cherry-pick state. It then prunes pool objects that no remaining ref reaches. It refuses while a registered Git directory is gone or carries a different consumer ID, because a moved checkout still borrows from the pool. store add <new path> re-registers a moved checkout, and store remove --forget <old path> releases a deleted one. See pruning before running it.
Supported submodule update --init commands prepare missing submodule Git directories with the same pool as reference. Recursive updates cover nested modules, including in new worktrees. Other Git commands and unsupported clone forms pass through to native Git, including local source paths, shallow or partial clones, explicit reference options, and SHA-256 repositories.
The checkout depends on the pool. See the storage guide before moving or deleting it.
Storage reports
git-dedup --stats clone and git-dedup store add --stats print a storage report to stderr. The report shows whether the pool already existed. Adoption reports compare private pack bytes before and after adoption. Clone reports identify use of Git alternates; they do not estimate disk savings.
Measurement is opt-in and scans local .pack, .idx, and .rev file metadata, without traversing Git objects. It excludes loose objects. These are logical file-size estimates, not measured disk blocks reclaimed. The first use populates the pool and can increase total disk use. Plain Git fallback does not print a report.