git-pull

Examples (TL;DR)

• Download changes from default remote repository and merge it: git pull
• Download changes from default remote repository and use fast forward: git pull --rebase
• Download changes from given remote repository and branch, then merge them into HEAD: git pull remote_name branch

tldr.sh

Synopsis

git pull [<options>] [<repository> [<refspec>...]]

Description

Incorporates changes from a remote repository into the current branch. In its default mode, git pull is shorthand for git fetch followed by git merge FETCH_HEAD.

More precisely, git pull runs git fetch with the given parameters and calls git merge to merge the retrieved branch heads into the current branch. With --rebase, it runs git rebase instead of git merge.

<repository> should be the name of a remote repository as passed to git-fetch(1). <refspec> can name an arbitrary remote ref (for example, the name of a tag) or even a collection of refs with corresponding remote-tracking branches (e.g., refs/heads/*:refs/remotes/origin/*), but usually it is the name of a branch in the remote repository.

Default values for <repository> and <branch> are read from the "remote" and "merge" configuration for the current branch as set by git-branch(1) --track.

Assume the following history exists and the current branch is "master":

          A---B---C master on origin
         /
    D---E---F---G master
        ^
        origin/master in your repository

Then "git pull" will fetch and replay the changes from the remote master branch since it diverged from the local master (i.e., E) until its current commit (C) on top of master and record the result in a new commit along with the names of the two parent commits and a log message from the user describing the changes.

          A---B---C origin/master
         /         \
    D---E---F---G---H master

See git-merge(1) for details, including how conflicts are presented and handled.

In Git 1.7.0 or later, to cancel a conflicting merge, use git reset --merge. Warning: In older versions of Git, running git pull with uncommitted changes is discouraged: while possible, it leaves you in a state that may be hard to back out of in the case of a conflict.

If any of the remote changes overlap with local uncommitted changes, the merge will be automatically canceled and the work tree untouched. It is generally best to get any local changes in working order before pulling or stash them away with git-stash(1).

Options

-q, --quiet

This is passed to both underlying git-fetch to squelch reporting of during transfer, and underlying git-merge to squelch output during merging.

-v, --verbose

Pass --verbose to git-fetch and git-merge.

--[no-]recurse-submodules[=yes|on-demand|no]

This option controls if new commits of all populated submodules should be fetched and updated, too (see git-config(1) and gitmodules(5)).

If the checkout is done via rebase, local submodule commits are rebased as well.

If the update is done via merge, the submodule conflicts are resolved and checked out.

Git Urls

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

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

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

The following syntaxes may be used with them:

• ssh://[user@]host.xz[:port]/path/to/repo.git/
• git://host.xz[:port]/path/to/repo.git/
• http[s]://host.xz[:port]/path/to/repo.git/
• ftp[s]://host.xz[:port]/path/to/repo.git/

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

• [user@]host.xz:path/to/repo.git/

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

The ssh and git protocols additionally support ~username expansion:

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

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

• /path/to/repo.git/
• file:///path/to/repo.git/

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

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

• <transport>::<address>

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

• a remote in the Git configuration file: $GIT_DIR/config,
• a file in the $GIT_DIR/remotes directory, or
• a file in the $GIT_DIR/branches directory.

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

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

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

        <url>#<head>

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

        HEAD:refs/heads/<head>

Merge Strategies

The merge mechanism (git merge and git pull commands) allows the backend merge strategies to be chosen with -s option. Some strategies can also take their own options, which can be passed by giving -X<option> arguments to git merge and/or git pull.

resolve

This can only resolve two heads (i.e. the current branch and another branch you pulled from) using a 3-way merge algorithm. It tries to carefully detect criss-cross merge ambiguities and is considered generally safe and fast.

recursive

This can only resolve two heads using a 3-way merge algorithm. When there is more than one common ancestor that can be used for 3-way merge, it creates a merged tree of the common ancestors and uses that as the reference tree for the 3-way merge. This has been reported to result in fewer merge conflicts without causing mismerges by tests done on actual merge commits taken from Linux 2.6 kernel development history. Additionally this can detect and handle merges involving renames, but currently cannot make use of detected copies. This is the default merge strategy when pulling or merging one branch.

The recursive strategy can take the following options:

ours

This option forces conflicting hunks to be auto-resolved cleanly by favoring our version. Changes from the other tree that do not conflict with our side are reflected to the merge result. For a binary file, the entire contents are taken from our side.

This should not be confused with the ours merge strategy, which does not even look at what the other tree contains at all. It discards everything the other tree did, declaring our history contains all that happened in it.

theirs

This is the opposite of ours; note that, unlike ours, there is no theirs merge strategy to confuse this merge option with.

patience

With this option, merge-recursive spends a little extra time to avoid mismerges that sometimes occur due to unimportant matching lines (e.g., braces from distinct functions). Use this when the branches to be merged have diverged wildly. See also git-diff(1) --patience.

diff-algorithm=[patience|minimal|histogram|myers]

Tells merge-recursive to use a different diff algorithm, which can help avoid mismerges that occur due to unimportant matching lines (such as braces from distinct functions). See also git-diff(1) --diff-algorithm.

ignore-space-change, ignore-all-space, ignore-space-at-eol, ignore-cr-at-eol

Treats lines with the indicated type of whitespace change as unchanged for the sake of a three-way merge. Whitespace changes mixed with other changes to a line are not ignored. See also git-diff(1) -b, -w, --ignore-space-at-eol, and --ignore-cr-at-eol.

• If their version only introduces whitespace changes to a line, our version is used;
• If our version introduces whitespace changes but their version includes a substantial change, their version is used;
• Otherwise, the merge proceeds in the usual way.

renormalize

This runs a virtual check-out and check-in of all three stages of a file when resolving a three-way merge. This option is meant to be used when merging branches with different clean filters or end-of-line normalization rules. See "Merging branches with differing checkin/checkout attributes" in gitattributes(5) for details.

no-renormalize

Disables the renormalize option. This overrides the merge.renormalize configuration variable.

no-renames

Turn off rename detection. This overrides the merge.renames configuration variable. See also git-diff(1) --no-renames.

find-renames[=<n>]

Turn on rename detection, optionally setting the similarity threshold. This is the default. This overrides the merge.renames configuration variable. See also git-diff(1) --find-renames.

rename-threshold=<n>

Deprecated synonym for find-renames=<n>.

subtree[=<path>]

This option is a more advanced form of subtree strategy, where the strategy makes a guess on how two trees must be shifted to match with each other when merging. Instead, the specified path is prefixed (or stripped from the beginning) to make the shape of two trees to match.

octopus

This resolves cases with more than two heads, but refuses to do a complex merge that needs manual resolution. It is primarily meant to be used for bundling topic branch heads together. This is the default merge strategy when pulling or merging more than one branch.

ours

This resolves any number of heads, but the resulting tree of the merge is always that of the current branch head, effectively ignoring all changes from all other branches. It is meant to be used to supersede old development history of side branches. Note that this is different from the -Xours option to the recursive merge strategy.

subtree

This is a modified recursive strategy. When merging trees A and B, if B corresponds to a subtree of A, B is first adjusted to match the tree structure of A, instead of reading the trees at the same level. This adjustment is also done to the common ancestor tree.

With the strategies that use 3-way merge (including the default, recursive), if a change is made on both branches, but later reverted on one of the branches, that change will be present in the merged result; some people find this behavior confusing. It occurs because only the heads and the merge base are considered when performing a merge, not the individual commits. The merge algorithm therefore considers the reverted change as no change at all, and substitutes the changed version instead.

Default Behaviour

Often people use git pull without giving any parameter. Traditionally, this has been equivalent to saying git pull origin. However, when configuration branch.<name>.remote is present while on branch <name>, that value is used instead of origin.

In order to determine what URL to use to fetch from, the value of the configuration remote.<origin>.url is consulted and if there is not any such variable, the value on the URL: line in $GIT_DIR/remotes/<origin> is used.

In order to determine what remote branches to fetch (and optionally store in the remote-tracking branches) when the command is run without any refspec parameters on the command line, values of the configuration variable remote.<origin>.fetch are consulted, and if there aren’t any, $GIT_DIR/remotes/<origin> is consulted and its Pull: lines are used. In addition to the refspec formats described in the Options section, you can have a globbing refspec that looks like this:

refs/heads/*:refs/remotes/origin/*

A globbing refspec must have a non-empty RHS (i.e. must store what were fetched in remote-tracking branches), and its LHS and RHS must end with /*. The above specifies that all remote branches are tracked using remote-tracking branches in refs/remotes/origin/ hierarchy under the same name.

The rule to determine which remote branch to merge after fetching is a bit involved, in order not to break backward compatibility.

If explicit refspecs were given on the command line of git pull, they are all merged.

When no refspec was given on the command line, then git pull uses the refspec from the configuration or $GIT_DIR/remotes/<origin>. In such cases, the following rules apply:

1. If branch.<name>.merge configuration for the current branch <name> exists, that is the name of the branch at the remote site that is merged.
2. If the refspec is a globbing one, nothing is merged.
3. Otherwise the remote branch of the first refspec is merged.

Examples

• Update the remote-tracking branches for the repository you cloned from, then merge one of them into your current branch:

  $ git pull
  $ git pull origin

  Normally the branch merged in is the HEAD of the remote repository, but the choice is determined by the branch.<name>.remote and branch.<name>.merge options; see git-config(1) for details.

• Merge into the current branch the remote branch next:

  $ git pull origin next

  This leaves a copy of next temporarily in FETCH_HEAD, but does not update any remote-tracking branches. Using remote-tracking branches, the same can be done by invoking fetch and merge:

  $ git fetch origin
  $ git merge origin/next

If you tried a pull which resulted in complex conflicts and would want to start over, you can recover with git reset.

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-fetch(1), git-merge(1), git-config(1)

Git

Part of the git(1) suite

Referenced By

git(1), git-config(1), giteveryday(7), git-fetch(1), gitglossary(7), git-merge(1), git-push(1), gittutorial(7), gitworkflows(7), salt(7).