YoLinux.com: git-push manpage

GIT-PUSH(1) Git Manual GIT-PUSH(1)

NAME
git-push - Update remote refs along with associated objects

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>.

If <dst> doesn't start with refs/ (e.g. refs/heads/master) we will
try to infer where in refs/* on the destination <repository> it
belongs based on the type of <src> being pushed and whether <dst>
is ambiguous.

o If <dst> unambiguously refers to a ref on the <repository>
remote, then push to that ref.

o If <src> resolves to a ref starting with refs/heads/ or
refs/tags/, then prepend that to <dst>.

o Other ambiguity resolutions might be added in the future, but
for now any other cases will error out with an error indicating
what we tried, and depending on the
advice.pushUnqualifiedRefname configuration (see git-config(1))
suggest what refs/ namespace you may have wanted to push to.

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 their commit, and blindly pushing with --force will
lose their 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.

Alternatively, specifying --force-if-includes as an ancillary
option along with --force-with-lease[=<refname>] (i.e., without
saying what exact commit the ref on the remote side must be
pointing at, or which refs on the remote side are being protected)
at the time of "push" will verify if updates from the
remote-tracking refs that may have been implicitly updated in the
background are integrated locally before allowing a forced update.

-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.

--[no-]force-if-includes
Force an update only if the tip of the remote-tracking ref has been
integrated locally.

This option enables a check that verifies if the tip of the
remote-tracking ref is reachable from one of the "reflog" entries
of the local branch based in it for a rewrite. The check ensures
that any updates from the remote have been incorporated locally by
rejecting the forced update if that is not the case.

If the option is passed without specifying --force-with-lease, or
specified along with --force-with-lease=<refname>:<expect>, it is a
"no-op".

Specifying --no-force-if-includes disables this behavior.

--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:

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

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

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

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

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

o [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:

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

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

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

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

o /path/to/repo.git/

o 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.

git clone, git fetch and git pull, but not git push, will also accept a
suitable bundle file. See git-bundle(1).

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:

o <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(7) 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:

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

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

o 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> 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 (branch.<name>.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.

See the section describing <refspec>... above for a discussion of
the matching semantics.

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.

CONFIGURATION
Everything below this line in this section is selectively included from
the git-config(1) documentation. The content is the same as what's
found there:

push.autoSetupRemote
If set to "true" assume --set-upstream on default push when no
upstream tracking exists for the current branch; this option takes
effect with push.default options simple, upstream, and current. It
is useful if by default you want new branches to be pushed to the
default remote (like the behavior of push.default=current) and you
also want the upstream tracking to be set. Workflows most likely to
benefit from this option are simple central workflows where all
branches are expected to have the same name on the remote.

push.default
Defines the action git push should take if no refspec is given
(whether from the command-line, config, or elsewhere). Different
values are well-suited for specific workflows; for instance, in a
purely central workflow (i.e. the fetch source is equal to the push
destination), upstream is probably what you want. Possible values
are:

o nothing - do not push anything (error out) unless a refspec is
given. This is primarily meant for people who want to avoid
mistakes by always being explicit.

o current - push the current branch to update a branch with the
same name on the receiving end. Works in both central and
non-central workflows.

o upstream - push the current branch back to the branch whose
changes are usually integrated into the current branch (which
is called @{upstream}). This mode only makes sense if you are
pushing to the same repository you would normally pull from
(i.e. central workflow).

o tracking - This is a deprecated synonym for upstream.

o simple - pushes the current branch with the same name on the
remote.

If you are working on a centralized workflow (pushing to the
same repository you pull from, which is typically origin), then
you need to configure an upstream branch with the same name.

This mode is the default since Git 2.0, and is the safest
option suited for beginners.

o matching - push all branches having the same name on both ends.
This makes the repository you are pushing to remember the set
of branches that will be pushed out (e.g. if you always push
maint and master there and no other branches, the repository
you push to will have these two branches, and your local maint
and master will be pushed there).

To use this mode effectively, you have to make sure all the
branches you would push out are ready to be pushed out before
running git push, as the whole point of this mode is to allow
you to push all of the branches in one go. If you usually
finish work on only one branch and push out the result, while
other branches are unfinished, this mode is not for you. Also
this mode is not suitable for pushing into a shared central
repository, as other people may add new branches there, or
update the tip of existing branches outside your control.

This used to be the default, but not since Git 2.0 (simple is
the new default).

push.followTags
If set to true enable --follow-tags option by default. You may
override this configuration at time of push by specifying
--no-follow-tags.

push.gpgSign
May be set to a boolean value, or the string if-asked. A true value
causes all pushes to be GPG signed, as if --signed is passed to
git-push(1). The string if-asked causes pushes to be signed if the
server supports it, as if --signed=if-asked is passed to git push.
A false value may override a value from a lower-priority config
file. An explicit command-line flag always overrides this config
option.

push.pushOption
When no --push-option=<option> argument is given from the command
line, git push behaves as if each <value> of this variable is given
as --push-option=<value>.

This is a multi-valued variable, and an empty value can be used in
a higher priority configuration file (e.g. .git/config in a
repository) to clear the values inherited from a lower priority
configuration files (e.g. $HOME/.gitconfig).

Example:

/etc/gitconfig
push.pushoption = a
push.pushoption = b

~/.gitconfig
push.pushoption = c

repo/.git/config
push.pushoption =
push.pushoption = b

This will result in only b (a and c are cleared).

push.recurseSubmodules
Make sure all submodule commits used by the revisions to be pushed
are available on a remote-tracking branch. If the value is check
then 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 the value is on-demand then 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 the value
is no then default behavior of ignoring submodules when pushing is
retained. You may override this configuration at time of push by
specifying --recurse-submodules=check|on-demand|no. If not set, no
is used by default, unless submodule.recurse is set (in which case
a true value means on-demand).

push.useForceIfIncludes
If set to "true", it is equivalent to specifying
--force-if-includes as an option to git-push(1) in the command
line. Adding --no-force-if-includes at the time of push overrides
this configuration setting.

push.negotiate
If set to "true", attempt to reduce the size of the packfile sent
by rounds of negotiation in which the client and the server attempt
to find commits in common. If "false", Git will rely solely on the
server's ref advertisement to find commits in common.

push.useBitmaps
If set to "false", disable use of bitmaps for "git push" even if
pack.useBitmaps is "true", without preventing other git operations
from using bitmaps. Default is true.

GIT
Part of the git(1) suite

Git 2.38.4 05/16/2024 GIT-PUSH(1)

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