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NAME

       git-push - Update remote refs along with associated objects

SYNOPSIS

       git push [--all | --mirror | --tags] [--follow-tags] [--atomic] [-n | --dry-run] [--receive-pack=<git-receive-pack>]
                  [--repo=<repository>] [-f | --force] [-d | --delete] [--prune] [-v | --verbose]
                  [-u | --set-upstream] [-o <string> | --push-option=<string>]
                  [--[no-]signed|--signed=(true|false|if-asked)]
                  [--force-with-lease[=<refname>[:<expect>]]]
                  [--no-verify] [<repository> [<refspec>...]]

DESCRIPTION

       Updates remote refs using local refs, while sending objects necessary to complete the
       given refs.

       You can make interesting things happen to a repository every time you push into it, by
       setting up hooks there. See documentation for git-receive-pack(1).

       When the command line does not specify where to push with the <repository> argument,
       branch.*.remote configuration for the current branch is consulted to determine where to
       push. If the configuration is missing, it defaults to origin.

       When the command line does not specify what to push with <refspec>... arguments or --all,
       --mirror, --tags options, the command finds the default <refspec> by consulting
       remote.*.push configuration, and if it is not found, honors push.default configuration to
       decide what to push (See git-config(1) for the meaning of push.default).

       When neither the command-line nor the configuration specify what to push, the default
       behavior is used, which corresponds to the simple value for push.default: the current
       branch is pushed to the corresponding upstream branch, but as a safety measure, the push
       is aborted if the upstream branch does not have the same name as the local one.

OPTIONS

       <repository>
           The "remote" repository that is destination of a push operation. This parameter can be
           either a URL (see the section GIT URLS below) or the name of a remote (see the section
           REMOTES below).

       <refspec>...
           Specify what destination ref to update with what source object. The format of a
           <refspec> parameter is an optional plus +, followed by the source object <src>,
           followed by a colon :, followed by the destination ref <dst>.

           The <src> is often the name of the branch you would want to push, but it can be any
           arbitrary "SHA-1 expression", such as master~4 or HEAD (see gitrevisions(7)).

           The <dst> tells which ref on the remote side is updated with this push. Arbitrary
           expressions cannot be used here, an actual ref must be named. If git push
           [<repository>] without any <refspec> argument is set to update some ref at the
           destination with <src> with remote.<repository>.push configuration variable, :<dst>
           part can be omitted—such a push will update a ref that <src> normally updates without
           any <refspec> on the command line. Otherwise, missing :<dst> means to update the same
           ref as the <src>.

           The object referenced by <src> is used to update the <dst> reference on the remote
           side. Whether this is allowed depends on where in refs/* the <dst> reference lives as
           described in detail below, in those sections "update" means any modifications except
           deletes, which as noted after the next few sections are treated differently.

           The refs/heads/* namespace will only accept commit objects, and updates only if they
           can be fast-forwarded.

           The refs/tags/* namespace will accept any kind of object (as commits, trees and blobs
           can be tagged), and any updates to them will be rejected.

           It’s possible to push any type of object to any namespace outside of
           refs/{tags,heads}/*. In the case of tags and commits, these will be treated as if they
           were the commits inside refs/heads/* for the purposes of whether the update is
           allowed.

           I.e. a fast-forward of commits and tags outside refs/{tags,heads}/* is allowed, even
           in cases where what’s being fast-forwarded is not a commit, but a tag object which
           happens to point to a new commit which is a fast-forward of the commit the last tag
           (or commit) it’s replacing. Replacing a tag with an entirely different tag is also
           allowed, if it points to the same commit, as well as pushing a peeled tag, i.e.
           pushing the commit that existing tag object points to, or a new tag object which an
           existing commit points to.

           Tree and blob objects outside of refs/{tags,heads}/* will be treated the same way as
           if they were inside refs/tags/*, any update of them will be rejected.

           All of the rules described above about what’s not allowed as an update can be
           overridden by adding an the optional leading + to a refspec (or using --force command
           line option). The only exception to this is that no amount of forcing will make the
           refs/heads/* namespace accept a non-commit object. Hooks and configuration can also
           override or amend these rules, see e.g.  receive.denyNonFastForwards in git-config(1)
           and pre-receive and update in githooks(5).

           Pushing an empty <src> allows you to delete the <dst> ref from the remote repository.
           Deletions are always accepted without a leading + in the refspec (or --force), except
           when forbidden by configuration or hooks. See receive.denyDeletes in git-config(1) and
           pre-receive and update in githooks(5).

           The special refspec : (or +: to allow non-fast-forward updates) directs Git to push
           "matching" branches: for every branch that exists on the local side, the remote side
           is updated if a branch of the same name already exists on the remote side.

           tag <tag> means the same as refs/tags/<tag>:refs/tags/<tag>.

       --all
           Push all branches (i.e. refs under refs/heads/); cannot be used with other <refspec>.

       --prune
           Remove remote branches that don’t have a local counterpart. For example a remote
           branch tmp will be removed if a local branch with the same name doesn’t exist any
           more. This also respects refspecs, e.g.  git push --prune remote
           refs/heads/*:refs/tmp/* would make sure that remote refs/tmp/foo will be removed if
           refs/heads/foo doesn’t exist.

       --mirror
           Instead of naming each ref to push, specifies that all refs under refs/ (which
           includes but is not limited to refs/heads/, refs/remotes/, and refs/tags/) be mirrored
           to the remote repository. Newly created local refs will be pushed to the remote end,
           locally updated refs will be force updated on the remote end, and deleted refs will be
           removed from the remote end. This is the default if the configuration option
           remote.<remote>.mirror is set.

       -n, --dry-run
           Do everything except actually send the updates.

       --porcelain
           Produce machine-readable output. The output status line for each ref will be
           tab-separated and sent to stdout instead of stderr. The full symbolic names of the
           refs will be given.

       -d, --delete
           All listed refs are deleted from the remote repository. This is the same as prefixing
           all refs with a colon.

       --tags
           All refs under refs/tags are pushed, in addition to refspecs explicitly listed on the
           command line.

       --follow-tags
           Push all the refs that would be pushed without this option, and also push annotated
           tags in refs/tags that are missing from the remote but are pointing at commit-ish that
           are reachable from the refs being pushed. This can also be specified with
           configuration variable push.followTags. For more information, see push.followTags in
           git-config(1).

       --[no-]signed, --signed=(true|false|if-asked)
           GPG-sign the push request to update refs on the receiving side, to allow it to be
           checked by the hooks and/or be logged. If false or --no-signed, no signing will be
           attempted. If true or --signed, the push will fail if the server does not support
           signed pushes. If set to if-asked, sign if and only if the server supports signed
           pushes. The push will also fail if the actual call to gpg --sign fails. See git-
           receive-pack(1) for the details on the receiving end.

       --[no-]atomic
           Use an atomic transaction on the remote side if available. Either all refs are
           updated, or on error, no refs are updated. If the server does not support atomic
           pushes the push will fail.

       -o <option>, --push-option=<option>
           Transmit the given string to the server, which passes them to the pre-receive as well
           as the post-receive hook. The given string must not contain a NUL or LF character.
           When multiple --push-option=<option> are given, they are all sent to the other side in
           the order listed on the command line. When no --push-option=<option> is given from the
           command line, the values of configuration variable push.pushOption are used instead.

       --receive-pack=<git-receive-pack>, --exec=<git-receive-pack>
           Path to the git-receive-pack program on the remote end. Sometimes useful when pushing
           to a remote repository over ssh, and you do not have the program in a directory on the
           default $PATH.

       --[no-]force-with-lease, --force-with-lease=<refname>,
       --force-with-lease=<refname>:<expect>
           Usually, "git push" refuses to update a remote ref that is not an ancestor of the
           local ref used to overwrite it.

           This option overrides this restriction if the current value of the remote ref is the
           expected value. "git push" fails otherwise.

           Imagine that you have to rebase what you have already published. You will have to
           bypass the "must fast-forward" rule in order to replace the history you originally
           published with the rebased history. If somebody else built on top of your original
           history while you are rebasing, the tip of the branch at the remote may advance with
           her commit, and blindly pushing with --force will lose her work.

           This option allows you to say that you expect the history you are updating is what you
           rebased and want to replace. If the remote ref still points at the commit you
           specified, you can be sure that no other people did anything to the ref. It is like
           taking a "lease" on the ref without explicitly locking it, and the remote ref is
           updated only if the "lease" is still valid.

           --force-with-lease alone, without specifying the details, will protect all remote refs
           that are going to be updated by requiring their current value to be the same as the
           remote-tracking branch we have for them.

           --force-with-lease=<refname>, without specifying the expected value, will protect the
           named ref (alone), if it is going to be updated, by requiring its current value to be
           the same as the remote-tracking branch we have for it.

           --force-with-lease=<refname>:<expect> will protect the named ref (alone), if it is
           going to be updated, by requiring its current value to be the same as the specified
           value <expect> (which is allowed to be different from the remote-tracking branch we
           have for the refname, or we do not even have to have such a remote-tracking branch
           when this form is used). If <expect> is the empty string, then the named ref must not
           already exist.

           Note that all forms other than --force-with-lease=<refname>:<expect> that specifies
           the expected current value of the ref explicitly are still experimental and their
           semantics may change as we gain experience with this feature.

           "--no-force-with-lease" will cancel all the previous --force-with-lease on the command
           line.

           A general note on safety: supplying this option without an expected value, i.e. as
           --force-with-lease or --force-with-lease=<refname> interacts very badly with anything
           that implicitly runs git fetch on the remote to be pushed to in the background, e.g.
           git fetch origin on your repository in a cronjob.

           The protection it offers over --force is ensuring that subsequent changes your work
           wasn’t based on aren’t clobbered, but this is trivially defeated if some background
           process is updating refs in the background. We don’t have anything except the remote
           tracking info to go by as a heuristic for refs you’re expected to have seen & are
           willing to clobber.

           If your editor or some other system is running git fetch in the background for you a
           way to mitigate this is to simply set up another remote:

               git remote add origin-push $(git config remote.origin.url)
               git fetch origin-push

           Now when the background process runs git fetch origin the references on origin-push
           won’t be updated, and thus commands like:

               git push --force-with-lease origin-push

           Will fail unless you manually run git fetch origin-push. This method is of course
           entirely defeated by something that runs git fetch --all, in that case you’d need to
           either disable it or do something more tedious like:

               git fetch              # update 'master' from remote
               git tag base master    # mark our base point
               git rebase -i master   # rewrite some commits
               git push --force-with-lease=master:base master:master

           I.e. create a base tag for versions of the upstream code that you’ve seen and are
           willing to overwrite, then rewrite history, and finally force push changes to master
           if the remote version is still at base, regardless of what your local
           remotes/origin/master has been updated to in the background.

       -f, --force
           Usually, the command refuses to update a remote ref that is not an ancestor of the
           local ref used to overwrite it. Also, when --force-with-lease option is used, the
           command refuses to update a remote ref whose current value does not match what is
           expected.

           This flag disables these checks, and can cause the remote repository to lose commits;
           use it with care.

           Note that --force applies to all the refs that are pushed, hence using it with
           push.default set to matching or with multiple push destinations configured with
           remote.*.push may overwrite refs other than the current branch (including local refs
           that are strictly behind their remote counterpart). To force a push to only one
           branch, use a + in front of the refspec to push (e.g git push origin +master to force
           a push to the master branch). See the <refspec>...  section above for details.

       --repo=<repository>
           This option is equivalent to the <repository> argument. If both are specified, the
           command-line argument takes precedence.

       -u, --set-upstream
           For every branch that is up to date or successfully pushed, add upstream (tracking)
           reference, used by argument-less git-pull(1) and other commands. For more information,
           see branch.<name>.merge in git-config(1).

       --[no-]thin
           These options are passed to git-send-pack(1). A thin transfer significantly reduces
           the amount of sent data when the sender and receiver share many of the same objects in
           common. The default is --thin.

       -q, --quiet
           Suppress all output, including the listing of updated refs, unless an error occurs.
           Progress is not reported to the standard error stream.

       -v, --verbose
           Run verbosely.

       --progress
           Progress status is reported on the standard error stream by default when it is
           attached to a terminal, unless -q is specified. This flag forces progress status even
           if the standard error stream is not directed to a terminal.

       --no-recurse-submodules, --recurse-submodules=check|on-demand|only|no
           May be used to make sure all submodule commits used by the revisions to be pushed are
           available on a remote-tracking branch. If check is used Git will verify that all
           submodule commits that changed in the revisions to be pushed are available on at least
           one remote of the submodule. If any commits are missing the push will be aborted and
           exit with non-zero status. If on-demand is used all submodules that changed in the
           revisions to be pushed will be pushed. If on-demand was not able to push all necessary
           revisions it will also be aborted and exit with non-zero status. If only is used all
           submodules will be recursively pushed while the superproject is left unpushed. A value
           of no or using --no-recurse-submodules can be used to override the
           push.recurseSubmodules configuration variable when no submodule recursion is required.

       --[no-]verify
           Toggle the pre-push hook (see githooks(5)). The default is --verify, giving the hook a
           chance to prevent the push. With --no-verify, the hook is bypassed completely.

       -4, --ipv4
           Use IPv4 addresses only, ignoring IPv6 addresses.

       -6, --ipv6
           Use IPv6 addresses only, ignoring IPv4 addresses.

GIT URLS

       In general, URLs contain information about the transport protocol, the address of the
       remote server, and the path to the repository. Depending on the transport protocol, some
       of this information may be absent.

       Git supports ssh, git, http, and https protocols (in addition, ftp, and ftps can be used
       for fetching, but this is inefficient and deprecated; do not use it).

       The native transport (i.e. git:// URL) does no authentication and should be used with
       caution on unsecured networks.

       The following syntaxes may be used with them:

       ·   ssh://[user@]host.xz[:port]/path/to/repo.git/

       ·   git://host.xz[:port]/path/to/repo.git/

       ·   http[s]://host.xz[:port]/path/to/repo.git/

       ·   ftp[s]://host.xz[:port]/path/to/repo.git/

       An alternative scp-like syntax may also be used with the ssh protocol:

       ·   [user@]host.xz:path/to/repo.git/

       This syntax is only recognized if there are no slashes before the first colon. This helps
       differentiate a local path that contains a colon. For example the local path foo:bar could
       be specified as an absolute path or ./foo:bar to avoid being misinterpreted as an ssh url.

       The ssh and git protocols additionally support ~username expansion:

       ·   ssh://[user@]host.xz[:port]/~[user]/path/to/repo.git/

       ·   git://host.xz[:port]/~[user]/path/to/repo.git/

       ·   [user@]host.xz:/~[user]/path/to/repo.git/

       For local repositories, also supported by Git natively, the following syntaxes may be
       used:

       ·   /path/to/repo.git/

       ·   file:///path/to/repo.git/

       These two syntaxes are mostly equivalent, except when cloning, when the former implies
       --local option. See git-clone(1) for details.

       When Git doesn’t know how to handle a certain transport protocol, it attempts to use the
       remote-<transport> remote helper, if one exists. To explicitly request a remote helper,
       the following syntax may be used:

       ·   <transport>::<address>

       where <address> may be a path, a server and path, or an arbitrary URL-like string
       recognized by the specific remote helper being invoked. See gitremote-helpers(1) for
       details.

       If there are a large number of similarly-named remote repositories and you want to use a
       different format for them (such that the URLs you use will be rewritten into URLs that
       work), you can create a configuration section of the form:

                   [url "<actual url base>"]
                           insteadOf = <other url base>

       For example, with this:

                   [url "git://git.host.xz/"]
                           insteadOf = host.xz:/path/to/
                           insteadOf = work:

       a URL like "work:repo.git" or like "host.xz:/path/to/repo.git" will be rewritten in any
       context that takes a URL to be "git://git.host.xz/repo.git".

       If you want to rewrite URLs for push only, you can create a configuration section of the
       form:

                   [url "<actual url base>"]
                           pushInsteadOf = <other url base>

       For example, with this:

                   [url "ssh://example.org/"]
                           pushInsteadOf = git://example.org/

       a URL like "git://example.org/path/to/repo.git" will be rewritten to
       "ssh://example.org/path/to/repo.git" for pushes, but pulls will still use the original
       URL.

REMOTES

       The name of one of the following can be used instead of a URL as <repository> argument:

       ·   a remote in the Git configuration file: $GIT_DIR/config,

       ·   a file in the $GIT_DIR/remotes directory, or

       ·   a file in the $GIT_DIR/branches directory.

       All of these also allow you to omit the refspec from the command line because they each
       contain a refspec which git will use by default.

   Named remote in configuration file
       You can choose to provide the name of a remote which you had previously configured using
       git-remote(1), git-config(1) or even by a manual edit to the $GIT_DIR/config file. The URL
       of this remote will be used to access the repository. The refspec of this remote will be
       used by default when you do not provide a refspec on the command line. The entry in the
       config file would appear like this:

                   [remote "<name>"]
                           url = <url>
                           pushurl = <pushurl>
                           push = <refspec>
                           fetch = <refspec>

       The <pushurl> is used for pushes only. It is optional and defaults to <url>.

   Named file in $GIT_DIR/remotes
       You can choose to provide the name of a file in $GIT_DIR/remotes. The URL in this file
       will be used to access the repository. The refspec in this file will be used as default
       when you do not provide a refspec on the command line. This file should have the following
       format:

                   URL: one of the above URL format
                   Push: <refspec>
                   Pull: <refspec>

       Push: lines are used by git push and Pull: lines are used by git pull and git fetch.
       Multiple Push: and Pull: lines may be specified for additional branch mappings.

   Named file in $GIT_DIR/branches
       You can choose to provide the name of a file in $GIT_DIR/branches. The URL in this file
       will be used to access the repository. This file should have the following format:

                   <url>#<head>

       <url> is required; #<head> is optional.

       Depending on the operation, git will use one of the following refspecs, if you don’t
       provide one on the command line. <branch> is the name of this file in $GIT_DIR/branches
       and <head> defaults to master.

       git fetch uses:

                   refs/heads/<head>:refs/heads/<branch>

       git push uses:

                   HEAD:refs/heads/<head>

OUTPUT

       The output of "git push" depends on the transport method used; this section describes the
       output when pushing over the Git protocol (either locally or via ssh).

       The status of the push is output in tabular form, with each line representing the status
       of a single ref. Each line is of the form:

            <flag> <summary> <from> -> <to> (<reason>)

       If --porcelain is used, then each line of the output is of the form:

            <flag> \t <from>:<to> \t <summary> (<reason>)

       The status of up-to-date refs is shown only if --porcelain or --verbose option is used.

       flag
           A single character indicating the status of the ref:

           (space)
               for a successfully pushed fast-forward;

           +
               for a successful forced update;

           -
               for a successfully deleted ref;

           *
               for a successfully pushed new ref;

           !
               for a ref that was rejected or failed to push; and

           =
               for a ref that was up to date and did not need pushing.

       summary
           For a successfully pushed ref, the summary shows the old and new values of the ref in
           a form suitable for using as an argument to git log (this is <old>..<new> in most
           cases, and <old>...<new> for forced non-fast-forward updates).

           For a failed update, more details are given:

           rejected
               Git did not try to send the ref at all, typically because it is not a fast-forward
               and you did not force the update.

           remote rejected
               The remote end refused the update. Usually caused by a hook on the remote side, or
               because the remote repository has one of the following safety options in effect:
               receive.denyCurrentBranch (for pushes to the checked out branch),
               receive.denyNonFastForwards (for forced non-fast-forward updates),
               receive.denyDeletes or receive.denyDeleteCurrent. See git-config(1).

           remote failure
               The remote end did not report the successful update of the ref, perhaps because of
               a temporary error on the remote side, a break in the network connection, or other
               transient error.

       from
           The name of the local ref being pushed, minus its refs/<type>/ prefix. In the case of
           deletion, the name of the local ref is omitted.

       to
           The name of the remote ref being updated, minus its refs/<type>/ prefix.

       reason
           A human-readable explanation. In the case of successfully pushed refs, no explanation
           is needed. For a failed ref, the reason for failure is described.

NOTE ABOUT FAST-FORWARDS

       When an update changes a branch (or more in general, a ref) that used to point at commit A
       to point at another commit B, it is called a fast-forward update if and only if B is a
       descendant of A.

       In a fast-forward update from A to B, the set of commits that the original commit A built
       on top of is a subset of the commits the new commit B builds on top of. Hence, it does not
       lose any history.

       In contrast, a non-fast-forward update will lose history. For example, suppose you and
       somebody else started at the same commit X, and you built a history leading to commit B
       while the other person built a history leading to commit A. The history looks like this:

                 B
                /
            ---X---A

       Further suppose that the other person already pushed changes leading to A back to the
       original repository from which you two obtained the original commit X.

       The push done by the other person updated the branch that used to point at commit X to
       point at commit A. It is a fast-forward.

       But if you try to push, you will attempt to update the branch (that now points at A) with
       commit B. This does not fast-forward. If you did so, the changes introduced by commit A
       will be lost, because everybody will now start building on top of B.

       The command by default does not allow an update that is not a fast-forward to prevent such
       loss of history.

       If you do not want to lose your work (history from X to B) or the work by the other person
       (history from X to A), you would need to first fetch the history from the repository,
       create a history that contains changes done by both parties, and push the result back.

       You can perform "git pull", resolve potential conflicts, and "git push" the result. A "git
       pull" will create a merge commit C between commits A and B.

                 B---C
                /   /
            ---X---A

       Updating A with the resulting merge commit will fast-forward and your push will be
       accepted.

       Alternatively, you can rebase your change between X and B on top of A, with "git pull
       --rebase", and push the result back. The rebase will create a new commit D that builds the
       change between X and B on top of A.

                 B   D
                /   /
            ---X---A

       Again, updating A with this commit will fast-forward and your push will be accepted.

       There is another common situation where you may encounter non-fast-forward rejection when
       you try to push, and it is possible even when you are pushing into a repository nobody
       else pushes into. After you push commit A yourself (in the first picture in this section),
       replace it with "git commit --amend" to produce commit B, and you try to push it out,
       because forgot that you have pushed A out already. In such a case, and only if you are
       certain that nobody in the meantime fetched your earlier commit A (and started building on
       top of it), you can run "git push --force" to overwrite it. In other words, "git push
       --force" is a method reserved for a case where you do mean to lose history.

EXAMPLES

       git push
           Works like git push <remote>, where <remote> is the current branch’s remote (or
           origin, if no remote is configured for the current branch).

       git push origin
           Without additional configuration, pushes the current branch to the configured upstream
           (remote.origin.merge configuration variable) if it has the same name as the current
           branch, and errors out without pushing otherwise.

           The default behavior of this command when no <refspec> is given can be configured by
           setting the push option of the remote, or the push.default configuration variable.

           For example, to default to pushing only the current branch to origin use git config
           remote.origin.push HEAD. Any valid <refspec> (like the ones in the examples below) can
           be configured as the default for git push origin.

       git push origin :
           Push "matching" branches to origin. See <refspec> in the OPTIONS section above for a
           description of "matching" branches.

       git push origin master
           Find a ref that matches master in the source repository (most likely, it would find
           refs/heads/master), and update the same ref (e.g.  refs/heads/master) in origin
           repository with it. If master did not exist remotely, it would be created.

       git push origin HEAD
           A handy way to push the current branch to the same name on the remote.

       git push mothership master:satellite/master dev:satellite/dev
           Use the source ref that matches master (e.g.  refs/heads/master) to update the ref
           that matches satellite/master (most probably refs/remotes/satellite/master) in the
           mothership repository; do the same for dev and satellite/dev.

           This is to emulate git fetch run on the mothership using git push that is run in the
           opposite direction in order to integrate the work done on satellite, and is often
           necessary when you can only make connection in one way (i.e. satellite can ssh into
           mothership but mothership cannot initiate connection to satellite because the latter
           is behind a firewall or does not run sshd).

           After running this git push on the satellite machine, you would ssh into the
           mothership and run git merge there to complete the emulation of git pull that were run
           on mothership to pull changes made on satellite.

       git push origin HEAD:master
           Push the current branch to the remote ref matching master in the origin repository.
           This form is convenient to push the current branch without thinking about its local
           name.

       git push origin master:refs/heads/experimental
           Create the branch experimental in the origin repository by copying the current master
           branch. This form is only needed to create a new branch or tag in the remote
           repository when the local name and the remote name are different; otherwise, the ref
           name on its own will work.

       git push origin :experimental
           Find a ref that matches experimental in the origin repository (e.g.
           refs/heads/experimental), and delete it.

       git push origin +dev:master
           Update the origin repository’s master branch with the dev branch, allowing
           non-fast-forward updates.  This can leave unreferenced commits dangling in the origin
           repository.  Consider the following situation, where a fast-forward is not possible:

                           o---o---o---A---B  origin/master
                                    \
                                     X---Y---Z  dev

           The above command would change the origin repository to

                                     A---B  (unnamed branch)
                                    /
                           o---o---o---X---Y---Z  master

           Commits A and B would no longer belong to a branch with a symbolic name, and so would
           be unreachable. As such, these commits would be removed by a git gc command on the
           origin repository.

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