rebase --root: demonstrate a bug while amending root commit messages

[git.git] / Documentation / git-fetch.txt

git-fetch(1)
============

NAME
----
git-fetch - Download objects and refs from another repository


SYNOPSIS
--------
[verse]
'git fetch' [<options>] [<repository> [<refspec>...]]
'git fetch' [<options>] <group>
'git fetch' --multiple [<options>] [(<repository> | <group>)...]
'git fetch' --all [<options>]


DESCRIPTION
-----------
Fetch branches and/or tags (collectively, "refs") from one or more
other repositories, along with the objects necessary to complete their
histories.  Remote-tracking branches are updated (see the description
of <refspec> below for ways to control this behavior).

By default, any tag that points into the histories being fetched is
also fetched; the effect is to fetch tags that
point at branches that you are interested in.  This default behavior
can be changed by using the --tags or --no-tags options or by
configuring remote.<name>.tagOpt.  By using a refspec that fetches tags
explicitly, you can fetch tags that do not point into branches you
are interested in as well.

'git fetch' can fetch from either a single named repository or URL,
or from several repositories at once if <group> is given and
there is a remotes.<group> entry in the configuration file.
(See linkgit:git-config[1]).

When no remote is specified, by default the `origin` remote will be used,
unless there's an upstream branch configured for the current branch.

The names of refs that are fetched, together with the object names
they point at, are written to `.git/FETCH_HEAD`.  This information
may be used by scripts or other git commands, such as linkgit:git-pull[1].

OPTIONS
-------
include::fetch-options.txt[]

include::pull-fetch-param.txt[]

include::urls-remotes.txt[]


CONFIGURED REMOTE-TRACKING BRANCHES[[CRTB]]
-------------------------------------------

You often interact with the same remote repository by
regularly and repeatedly fetching from it.  In order to keep track
of the progress of such a remote repository, `git fetch` allows you
to configure `remote.<repository>.fetch` configuration variables.

Typically such a variable may look like this:

------------------------------------------------
[remote "origin"]
        fetch = +refs/heads/*:refs/remotes/origin/*
------------------------------------------------

This configuration is used in two ways:

* When `git fetch` is run without specifying what branches
  and/or tags to fetch on the command line, e.g. `git fetch origin`
  or `git fetch`, `remote.<repository>.fetch` values are used as
  the refspecs--they specify which refs to fetch and which local refs
  to update.  The example above will fetch
  all branches that exist in the `origin` (i.e. any ref that matches
  the left-hand side of the value, `refs/heads/*`) and update the
  corresponding remote-tracking branches in the `refs/remotes/origin/*`
  hierarchy.

* When `git fetch` is run with explicit branches and/or tags
  to fetch on the command line, e.g. `git fetch origin master`, the
  <refspec>s given on the command line determine what are to be
  fetched (e.g. `master` in the example,
  which is a short-hand for `master:`, which in turn means
  "fetch the 'master' branch but I do not explicitly say what
  remote-tracking branch to update with it from the command line"),
  and the example command will
  fetch _only_ the 'master' branch.  The `remote.<repository>.fetch`
  values determine which
  remote-tracking branch, if any, is updated.  When used in this
  way, the `remote.<repository>.fetch` values do not have any
  effect in deciding _what_ gets fetched (i.e. the values are not
  used as refspecs when the command-line lists refspecs); they are
  only used to decide _where_ the refs that are fetched are stored
  by acting as a mapping.

The latter use of the `remote.<repository>.fetch` values can be
overridden by giving the `--refmap=<refspec>` parameter(s) on the
command line.

PRUNING
-------

Git has a default disposition of keeping data unless it's explicitly
thrown away; this extends to holding onto local references to branches
on remotes that have themselves deleted those branches.

If left to accumulate, these stale references might make performance
worse on big and busy repos that have a lot of branch churn, and
e.g. make the output of commands like `git branch -a --contains
<commit>` needlessly verbose, as well as impacting anything else
that'll work with the complete set of known references.

These remote-tracking references can be deleted as a one-off with
either of:

------------------------------------------------
# While fetching
$ git fetch --prune <name>

# Only prune, don't fetch
$ git remote prune <name>
------------------------------------------------

To prune references as part of your normal workflow without needing to
remember to run that, set `fetch.prune` globally, or
`remote.<name>.prune` per-remote in the config. See
linkgit:git-config[1].

Here's where things get tricky and more specific. The pruning feature
doesn't actually care about branches, instead it'll prune local <->
remote-references as a function of the refspec of the remote (see
`<refspec>` and <<CRTB,CONFIGURED REMOTE-TRACKING BRANCHES>> above).

Therefore if the refspec for the remote includes
e.g. `refs/tags/*:refs/tags/*`, or you manually run e.g. `git fetch
--prune <name> "refs/tags/*:refs/tags/*"` it won't be stale remote
tracking branches that are deleted, but any local tag that doesn't
exist on the remote.

This might not be what you expect, i.e. you want to prune remote
`<name>`, but also explicitly fetch tags from it, so when you fetch
from it you delete all your local tags, most of which may not have
come from the `<name>` remote in the first place.

So be careful when using this with a refspec like
`refs/tags/*:refs/tags/*`, or any other refspec which might map
references from multiple remotes to the same local namespace.

Since keeping up-to-date with both branches and tags on the remote is
a common use-case the `--prune-tags` option can be supplied along with
`--prune` to prune local tags that don't exist on the remote, and
force-update those tags that differ. Tag pruning can also be enabled
with `fetch.pruneTags` or `remote.<name>.pruneTags` in the config. See
linkgit:git-config[1].

The `--prune-tags` option is equivalent to having
`refs/tags/*:refs/tags/*` declared in the refspecs of the remote. This
can lead to some seemingly strange interactions:

------------------------------------------------
# These both fetch tags
$ git fetch --no-tags origin 'refs/tags/*:refs/tags/*'
$ git fetch --no-tags --prune-tags origin
------------------------------------------------

The reason it doesn't error out when provided without `--prune` or its
config versions is for flexibility of the configured versions, and to
maintain a 1=1 mapping between what the command line flags do, and
what the configuration versions do.

It's reasonable to e.g. configure `fetch.pruneTags=true` in
`~/.gitconfig` to have tags pruned whenever `git fetch --prune` is
run, without making every invocation of `git fetch` without `--prune`
an error.

Pruning tags with `--prune-tags` also works when fetching a URL
instead of a named remote. These will all prune tags not found on
origin:

------------------------------------------------
$ git fetch origin --prune --prune-tags
$ git fetch origin --prune 'refs/tags/*:refs/tags/*'
$ git fetch <url of origin> --prune --prune-tags
$ git fetch <url of origin> --prune 'refs/tags/*:refs/tags/*'
------------------------------------------------

OUTPUT
------

The output of "git fetch" depends on the transport method used; this
section describes the output when fetching over the Git protocol
(either locally or via ssh) and Smart HTTP protocol.

The status of the fetch 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>]
-------------------------------

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

In compact output mode, specified with configuration variable
fetch.output, if either entire `<from>` or `<to>` is found in the
other string, it will be substituted with `*` in the other string. For
example, `master -> origin/master` becomes `master -> origin/*`.

flag::
        A single character indicating the status of the ref:
(space);; for a successfully fetched fast-forward;
`+`;; for a successful forced update;
`-`;; for a successfully pruned ref;
`t`;; for a successful tag update;
`*`;; for a successfully fetched new ref;
`!`;; for a ref that was rejected or failed to update; and
`=`;; for a ref that was up to date and did not need fetching.

summary::
        For a successfully fetched 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).

from::
        The name of the remote ref being fetched from, minus its
        `refs/<type>/` prefix. In the case of deletion, the name of
        the remote ref is "(none)".

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

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

EXAMPLES
--------

* Update the remote-tracking branches:
+
------------------------------------------------
$ git fetch origin
------------------------------------------------
+
The above command copies all branches from the remote refs/heads/
namespace and stores them to the local refs/remotes/origin/ namespace,
unless the branch.<name>.fetch option is used to specify a non-default
refspec.

* Using refspecs explicitly:
+
------------------------------------------------
$ git fetch origin +pu:pu maint:tmp
------------------------------------------------
+
This updates (or creates, as necessary) branches `pu` and `tmp` in
the local repository by fetching from the branches (respectively)
`pu` and `maint` from the remote repository.
+
The `pu` branch will be updated even if it is does not fast-forward,
because it is prefixed with a plus sign; `tmp` will not be.

* Peek at a remote's branch, without configuring the remote in your local
repository:
+
------------------------------------------------
$ git fetch git://git.kernel.org/pub/scm/git/git.git maint
$ git log FETCH_HEAD
------------------------------------------------
+
The first command fetches the `maint` branch from the repository at
`git://git.kernel.org/pub/scm/git/git.git` and the second command uses
`FETCH_HEAD` to examine the branch with linkgit:git-log[1].  The fetched
objects will eventually be removed by git's built-in housekeeping (see
linkgit:git-gc[1]).

include::transfer-data-leaks.txt[]

BUGS
----
Using --recurse-submodules can only fetch new commits in already checked
out submodules right now. When e.g. upstream added a new submodule in the
just fetched commits of the superproject the submodule itself can not be
fetched, making it impossible to check out that submodule later without
having to do a fetch again. This is expected to be fixed in a future Git
version.

SEE ALSO
--------
linkgit:git-pull[1]

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