# gitnamespaces

## NAME



           gitnamespaces - Git namespaces
    


## SYNOPSIS



           GIT_NAMESPACE=<namespace> _git upload-pack_
           GIT_NAMESPACE=<namespace> _git receive-pack_
    


## DESCRIPTION



           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'
    


## SECURITY



           The fetch and push protocols are not designed to prevent one side
           from stealing data from the other repository that was not intended
           to be shared. If you have private data that you need to protect
           from a malicious peer, your best option is to store it in another
           repository. This applies to both clients and servers. In
           particular, namespaces on a server are not effective for read
           access control; you should only grant read access to a namespace
           to clients that you would trust with read access to the entire
           repository.
    
           The known attack vectors are as follows:
    
            1. The victim sends "have" lines advertising the IDs of objects
               it has that are not explicitly intended to be shared but can
               be used to optimize the transfer if the peer also has them.
               The attacker chooses an object ID X to steal and sends a ref
               to X, but isn’t required to send the content of X because the
               victim already has it. Now the victim believes that the
               attacker has X, and it sends the content of X back to the
               attacker later. (This attack is most straightforward for a
               client to perform on a server, by creating a ref to X in the
               namespace the client has access to and then fetching it. The
               most likely way for a server to perform it on a client is to
               "merge" X into a public branch and hope that the user does
               additional work on this branch and pushes it back to the
               server without noticing the merge.)
    
            2. As in #1, the attacker chooses an object ID X to steal. The
               victim sends an object Y that the attacker already has, and
               the attacker falsely claims to have X and not Y, so the victim
               sends Y as a delta against X. The delta reveals regions of X
               that are similar to Y to the attacker.
    


## GIT



           Part of the git(1) suite
    


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