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gitnamespaces - Git namespaces
GIT_NAMESPACE=<namespace> git upload-pack
GIT_NAMESPACE=<namespace> git receive-pack
Git supports dividing the refs of a single repository into multiple
namespaces, each of which has its own branches, tags, and HEAD. Git can
expose each namespace as an independent repository to pull from and
push to, while sharing the object store, and exposing all the refs to
operations such as git-gc(1).
Storing multiple repositories as namespaces of a single repository
avoids storing duplicate copies of the same objects, such as when
storing multiple branches of the same source. The alternates mechanism
provides similar support for avoiding duplicates, but alternates do not
prevent duplication between new objects added to the repositories
without ongoing maintenance, while namespaces do.
To specify a namespace, set the GIT_NAMESPACE environment variable to
the namespace. For each ref namespace, git stores the corresponding
refs in a directory under refs/namespaces/. For example,
GIT_NAMESPACE=foo will store refs under refs/namespaces/foo/. You can
also specify namespaces via the --namespace option to git(1).
Note that namespaces which include a / will expand to a hierarchy of
namespaces; for example, GIT_NAMESPACE=foo/bar will store refs under
refs/namespaces/foo/refs/namespaces/bar/. This makes paths in
GIT_NAMESPACE behave hierarchically, so that cloning with
GIT_NAMESPACE=foo/bar produces the same result as cloning with
GIT_NAMESPACE=foo and cloning from that repo with GIT_NAMESPACE=bar. It
also avoids ambiguity with strange namespace paths such as
foo/refs/heads/, which could otherwise generate directory/file
conflicts within the refs directory.
git-upload-pack(1) and git-receive-pack(1) rewrite the names of refs as
specified by GIT_NAMESPACE. git-upload-pack and git-receive-pack will
ignore all references outside the specified namespace.
The smart HTTP server, git-http-backend(1), will pass GIT_NAMESPACE
through to the backend programs; see git-http-backend(1) for sample
configuration to expose repository namespaces as repositories.
For a simple local test, you can use git-remote-ext(1):
git clone ext::'git --namespace=foo %s /tmp/prefixed.git'
Anyone with access to any namespace within a repository can potentially
access objects from any other namespace stored in the same repository.
You can’t directly say "give me object ABCD" if you don’t have a ref to
it, but you can do some other sneaky things like:
1. Claiming to push ABCD, at which point the server will optimize out
the need for you to actually send it. Now you have a ref to ABCD
and can fetch it (claiming not to have it, of course).
2. Requesting other refs, claiming that you have ABCD, at which point
the server may generate deltas against ABCD.
None of this causes a problem if you only host public repositories, or
if everyone who may read one namespace may also read everything in
every other namespace (for instance, if everyone in an organization has
read permission to every repository).