cherry-pick: fix docs describing handling of empty commits

[git/gitweb.git] / Documentation / git-push.txt

git-push(1)
===========

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


SYNOPSIS
--------
[verse]
'git push' [--all | --mirror | --tags] [--follow-tags] [-n | --dry-run] [--receive-pack=<git-receive-pack>]
           [--repo=<repository>] [-f | --force] [--prune] [-v | --verbose] [-u | --set-upstream]
           [--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 linkgit: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 gitlink:git-config[1] for the meaning of `push.default`).


OPTIONS[[OPTIONS]]
------------------
<repository>::
        The "remote" repository that is destination of a push
        operation.  This parameter can be either a URL
        (see the section <<URLS,GIT URLS>> below) or the name
        of a remote (see the section <<REMOTES,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 linkgit: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.  By default this is only allowed if <dst> is not
a tag (annotated or lightweight), and then only if it can fast-forward
<dst>.  By having the optional leading `+`, you can tell Git to update
the <dst> ref even if it is not allowed by default (e.g., it is not a
fast-forward.)  This does *not* attempt to merge <src> into <dst>.  See
EXAMPLES below for details.
+
`tag <tag>` means the same as `refs/tags/<tag>:refs/tags/<tag>`.
+
Pushing an empty <src> allows you to delete the <dst> ref from
the remote repository.
+
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.

--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.

--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.

--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 bypasses the check, but instead requires that the
current value of the ref to be 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 you update the ref while
making sure that your earlier "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, unless specified with a `--force-with-lease=<refname>:<expect>`
option that explicitly states what the expected value is.
+
`--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).
+
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.

-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 only relevant if no <repository> argument is
        passed in the invocation. In this case, 'git push' derives the
        remote name from the current branch: If it tracks a remote
        branch, then that remote repository is pushed to. Otherwise,
        the name "origin" is used. For this latter case, this option
        can be used to override the name "origin". In other words,
        the difference between these two commands
+
--------------------------
git push public         #1
git push --repo=public  #2
--------------------------
+
is that #1 always pushes to "public" whereas #2 pushes to "public"
only if the current branch does not track a remote branch. This is
useful if you write an alias or script around 'git push'.

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

--[no-]thin::
        These options are passed to linkgit: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.

--recurse-submodules=check|on-demand::
        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.

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


include::urls-remotes.txt[]

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 linkgit: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,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.

GIT
---
Part of the linkgit:git[1] suite