GIT-FETCH(1)



GIT-FETCH(1)                      Git Manual                      GIT-FETCH(1)

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

SYNOPSIS
       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 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 git-pull(1).

OPTIONS
       --all
           Fetch all remotes.

       -a, --append
           Append ref names and object names of fetched refs to the existing
           contents of .git/FETCH_HEAD. Without this option old data in
           .git/FETCH_HEAD will be overwritten.

       --depth=<depth>
           Limit fetching to the specified number of commits from the tip of
           each remote branch history. If fetching to a shallow repository
           created by git clone with --depth=<depth> option (see git-
           clone(1)), deepen or shorten the history to the specified number of
           commits. Tags for the deepened commits are not fetched.

       --deepen=<depth>
           Similar to --depth, except it specifies the number of commits from
           the current shallow boundary instead of from the tip of each remote
           branch history.

       --shallow-since=<date>
           Deepen or shorten the history of a shallow repository to include
           all reachable commits after <date>.

       --shallow-exclude=<revision>
           Deepen or shorten the history of a shallow repository to exclude
           commits reachable from a specified remote branch or tag. This
           option can be specified multiple times.

       --unshallow
           If the source repository is complete, convert a shallow repository
           to a complete one, removing all the limitations imposed by shallow
           repositories.

           If the source repository is shallow, fetch as much as possible so
           that the current repository has the same history as the source
           repository.

       --update-shallow
           By default when fetching from a shallow repository, git fetch
           refuses refs that require updating .git/shallow. This option
           updates .git/shallow and accept such refs.

       --negotiation-tip=<commit|glob>
           By default, Git will report, to the server, commits reachable from
           all local refs to find common commits in an attempt to reduce the
           size of the to-be-received packfile. If specified, Git will only
           report commits reachable from the given tips. This is useful to
           speed up fetches when the user knows which local ref is likely to
           have commits in common with the upstream ref being fetched.

           This option may be specified more than once; if so, Git will report
           commits reachable from any of the given commits.

           The argument to this option may be a glob on ref names, a ref, or
           the (possibly abbreviated) SHA-1 of a commit. Specifying a glob is
           equivalent to specifying this option multiple times, one for each
           matching ref name.

           See also the fetch.negotiationAlgorithm configuration variable
           documented in git-config(1).

       --dry-run
           Show what would be done, without making any changes.

       -f, --force
           When git fetch is used with <src>:<dst> refspec it may refuse to
           update the local branch as discussed in the <refspec> part below.
           This option overrides that check.

       -k, --keep
           Keep downloaded pack.

       --multiple
           Allow several <repository> and <group> arguments to be specified.
           No <refspec>s may be specified.

       --[no-]auto-gc
           Run git gc --auto at the end to perform garbage collection if
           needed. This is enabled by default.

       --[no-]write-commit-graph
           Write a commit-graph after fetching. This overrides the config
           setting fetch.writeCommitGraph.

       -p, --prune
           Before fetching, remove any remote-tracking references that no
           longer exist on the remote. Tags are not subject to pruning if they
           are fetched only because of the default tag auto-following or due
           to a --tags option. However, if tags are fetched due to an explicit
           refspec (either on the command line or in the remote configuration,
           for example if the remote was cloned with the --mirror option),
           then they are also subject to pruning. Supplying --prune-tags is a
           shorthand for providing the tag refspec.

           See the PRUNING section below for more details.

       -P, --prune-tags
           Before fetching, remove any local tags that no longer exist on the
           remote if --prune is enabled. This option should be used more
           carefully, unlike --prune it will remove any local references
           (local tags) that have been created. This option is a shorthand for
           providing the explicit tag refspec along with --prune, see the
           discussion about that in its documentation.

           See the PRUNING section below for more details.

       -n, --no-tags
           By default, tags that point at objects that are downloaded from the
           remote repository are fetched and stored locally. This option
           disables this automatic tag following. The default behavior for a
           remote may be specified with the remote.<name>.tagOpt setting. See
           git-config(1).

       --refmap=<refspec>
           When fetching refs listed on the command line, use the specified
           refspec (can be given more than once) to map the refs to
           remote-tracking branches, instead of the values of remote.*.fetch
           configuration variables for the remote repository. Providing an
           empty <refspec> to the --refmap option causes Git to ignore the
           configured refspecs and rely entirely on the refspecs supplied as
           command-line arguments. See section on "Configured Remote-tracking
           Branches" for details.

       -t, --tags
           Fetch all tags from the remote (i.e., fetch remote tags refs/tags/*
           into local tags with the same name), in addition to whatever else
           would otherwise be fetched. Using this option alone does not
           subject tags to pruning, even if --prune is used (though tags may
           be pruned anyway if they are also the destination of an explicit
           refspec; see --prune).

       --recurse-submodules[=yes|on-demand|no]
           This option controls if and under what conditions new commits of
           populated submodules should be fetched too. It can be used as a
           boolean option to completely disable recursion when set to no or to
           unconditionally recurse into all populated submodules when set to
           yes, which is the default when this option is used without any
           value. Use on-demand to only recurse into a populated submodule
           when the superproject retrieves a commit that updates the
           submodule's reference to a commit that isn't already in the local
           submodule clone. By default, on-demand is used, unless
           fetch.recurseSubmodules is set (see git-config(1)).

       -j, --jobs=<n>
           Number of parallel children to be used for all forms of fetching.

           If the --multiple option was specified, the different remotes will
           be fetched in parallel. If multiple submodules are fetched, they
           will be fetched in parallel. To control them independently, use the
           config settings fetch.parallel and submodule.fetchJobs (see git-
           config(1)).

           Typically, parallel recursive and multi-remote fetches will be
           faster. By default fetches are performed sequentially, not in
           parallel.

       --no-recurse-submodules
           Disable recursive fetching of submodules (this has the same effect
           as using the --recurse-submodules=no option).

       --set-upstream
           If the remote is fetched successfully, pull and add upstream
           (tracking) reference, used by argument-less git-pull(1) and other
           commands. For more information, see branch.<name>.merge and
           branch.<name>.remote in git-config(1).

       --submodule-prefix=<path>
           Prepend <path> to paths printed in informative messages such as
           "Fetching submodule foo". This option is used internally when
           recursing over submodules.

       --recurse-submodules-default=[yes|on-demand]
           This option is used internally to temporarily provide a
           non-negative default value for the --recurse-submodules option. All
           other methods of configuring fetch's submodule recursion (such as
           settings in gitmodules(5) and git-config(1)) override this option,
           as does specifying --[no-]recurse-submodules directly.

       -u, --update-head-ok
           By default git fetch refuses to update the head which corresponds
           to the current branch. This flag disables the check. This is purely
           for the internal use for git pull to communicate with git fetch,
           and unless you are implementing your own Porcelain you are not
           supposed to use it.

       --upload-pack <upload-pack>
           When given, and the repository to fetch from is handled by git
           fetch-pack, --exec=<upload-pack> is passed to the command to
           specify non-default path for the command run on the other end.

       -q, --quiet
           Pass --quiet to git-fetch-pack and silence any other internally
           used git commands. Progress is not reported to the standard error
           stream.

       -v, --verbose
           Be verbose.

       --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.

       -o <option>, --server-option=<option>
           Transmit the given string to the server when communicating using
           protocol version 2. The given string must not contain a NUL or LF
           character. The server's handling of server options, including
           unknown ones, is server-specific. When multiple
           --server-option=<option> are given, they are all sent to the other
           side in the order listed on the command line.

       --show-forced-updates
           By default, git checks if a branch is force-updated during fetch.
           This can be disabled through fetch.showForcedUpdates, but the
           --show-forced-updates option guarantees this check occurs. See git-
           config(1).

       --no-show-forced-updates
           By default, git checks if a branch is force-updated during fetch.
           Pass --no-show-forced-updates or set fetch.showForcedUpdates to
           false to skip this check for performance reasons. If used during
           git-pull the --ff-only option will still check for forced updates
           before attempting a fast-forward update. See git-config(1).

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

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

       <repository>
           The "remote" repository that is the source of a fetch or pull
           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).

       <group>
           A name referring to a list of repositories as the value of
           remotes.<group> in the configuration file. (See git-config(1)).

       <refspec>
           Specifies which refs to fetch and which local refs to update. When
           no <refspec>s appear on the command line, the refs to fetch are
           read from remote.<repository>.fetch variables instead (see
           CONFIGURED REMOTE-TRACKING BRANCHES below).

           The format of a <refspec> parameter is an optional plus +, followed
           by the source <src>, followed by a colon :, followed by the
           destination ref <dst>. The colon can be omitted when <dst> is
           empty. <src> is typically a ref, but it can also be a fully spelled
           hex object name.

           tag <tag> means the same as refs/tags/<tag>:refs/tags/<tag>; it
           requests fetching everything up to the given tag.

           The remote ref that matches <src> is fetched, and if <dst> is not
           an empty string, an attempt is made to update the local ref that
           matches it.

           Whether that update is allowed without --force depends on the ref
           namespace it's being fetched to, the type of object being fetched,
           and whether the update is considered to be a fast-forward.
           Generally, the same rules apply for fetching as when pushing, see
           the <refspec>...  section of git-push(1) for what those are.
           Exceptions to those rules particular to git fetch are noted below.

           Until Git version 2.20, and unlike when pushing with git-push(1),
           any updates to refs/tags/* would be accepted without + in the
           refspec (or --force). When fetching, we promiscuously considered
           all tag updates from a remote to be forced fetches. Since Git
           version 2.20, fetching to update refs/tags/* works the same way as
           when pushing. I.e. any updates will be rejected without + in the
           refspec (or --force).

           Unlike when pushing with git-push(1), any updates outside of
           refs/{tags,heads}/* will be accepted without + in the refspec (or
           --force), whether that's swapping e.g. a tree object for a blob, or
           a commit for another commit that's doesn't have the previous commit
           as an ancestor etc.

           Unlike when pushing with git-push(1), there is no configuration
           which'll amend these rules, and nothing like a pre-fetch hook
           analogous to the pre-receive hook.

           As with pushing with git-push(1), 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.

               Note
               When the remote branch you want to fetch is known to be rewound
               and rebased regularly, it is expected that its new tip will not
               be descendant of its previous tip (as stored in your
               remote-tracking branch the last time you fetched). You would
               want to use the + sign to indicate non-fast-forward updates
               will be needed for such branches. There is no way to determine
               or declare that a branch will be made available in a repository
               with this behavior; the pulling user simply must know this is
               the expected usage pattern for a branch.

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>#<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>

CONFIGURED REMOTE-TRACKING BRANCHES
       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:

       o   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.

       o   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 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 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 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
       o   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.

       o   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 does not fast-forward,
           because it is prefixed with a plus sign; tmp will not be.

       o   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 git-log(1). The fetched
           objects will eventually be removed by git's built-in housekeeping
           (see git-gc(1)).

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.

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 cannot 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
       git-pull(1)

GIT
       Part of the git(1) suite

Git 2.27.0                        06/01/2020                      GIT-FETCH(1)

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