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git-submodule (draft)

NAME

git-submodule - Initialize, update or inspect submodules

SYNOPSIS

git submodule [--quiet] add [<options>] [--] <repository> [<path>]
git submodule [--quiet] status [--cached] [--recursive] [--] [<path>...]
git submodule [--quiet] init [--] [<path>...]
git submodule [--quiet] deinit [-f|--force] (--all|[--] <path>...)
git submodule [--quiet] update [<options>] [--] [<path>...]
git submodule [--quiet] summary [<options>] [--] [<path>...]
git submodule [--quiet] foreach [--recursive] <command>
git submodule [--quiet] sync [--recursive] [--] [<path>...]
git submodule [--quiet] absorbgitdirs [--] [<path>...]

DESCRIPTION

Inspects, updates and manages submodules.

A submodule allows you to keep another Git repository in a subdirectory of your repository. The other repository has its own history, which does not interfere with the history of the current repository. This can be used to have external dependencies such as third party libraries for example.

When cloning or pulling a repository containing submodules however, these will not be checked out by default; the init and update subcommands will maintain submodules checked out and at appropriate revision in your working tree.

Submodules are composed from a so-called gitlink tree entry in the main repository that refers to a particular commit object within the inner repository that is completely separate. A record in the .gitmodules (see linkgit:gitmodules[5]) file at the root of the source tree assigns a logical name to the submodule and describes the default URL the submodule shall be cloned from. The logical name can be used for overriding this URL within your local repository configuration (see submodule init).

Submodules are not to be confused with remotes, which are other repositories of the same project; submodules are meant for different projects you would like to make part of your source tree, while the history of the two projects still stays completely independent and you cannot modify the contents of the submodule from within the main project. If you want to merge the project histories and want to treat the aggregated whole as a single project from then on, you may want to add a remote for the other project and use the subtree merge strategy, instead of treating the other project as a submodule. Directories that come from both projects can be cloned and checked out as a whole if you choose to go that route.

COMMANDS

add [-b <branch>] [-f|--force] [--name <name>] [--reference <repository>] [--depth <depth>] [--] <repository> [<path>]

Add the given repository as a submodule at the given path to the changeset to be committed next to the current project: the current project is termed the “superproject”.

This requires at least one argument: <repository>. The optional argument <path> is the relative location for the cloned submodule to exist in the superproject. If <path> is not given, the “humanish” part of the source repository is used (“repo” for “/path/to/repo.git” and “foo” for “host.xz:foo/.git”). The <path> is also used as the submodule’s logical name in its configuration entries unless --name is used to specify a logical name.

<repository> is the URL of the new submodule’s origin repository. This may be either an absolute URL, or (if it begins with ./ or ../), the location relative to the superproject’s default remote repository (Please note that to specify a repository foo.git which is located right next to a superproject bar.git, you’ll have to use ../foo.git instead of ./foo.git - as one might expect when following the rules for relative URLs - because the evaluation of relative URLs in Git is identical to that of relative directories).

The default remote is the remote of the remote tracking branch of the current branch. If no such remote tracking branch exists or the HEAD is detached, “origin” is assumed to be the default remote. If the superproject doesn’t have a default remote configured the superproject is its own authoritative upstream and the current working directory is used instead.

<path> is the relative location for the cloned submodule to exist in the superproject. If <path> does not exist, then the submodule is created by cloning from the named URL. If <path> does exist and is already a valid Git repository, then this is added to the changeset without cloning. This second form is provided to ease creating a new submodule from scratch, and presumes the user will later push the submodule to the given URL.

In either case, the given URL is recorded into .gitmodules for use by subsequent users cloning the superproject. If the URL is given relative to the superproject’s repository, the presumption is the superproject and submodule repositories will be kept together in the same relative location, and only the superproject’s URL needs to be provided: git-submodule will correctly locate the submodule using the relative URL in .gitmodules.

status [--cached] [--recursive] [--] [<path>...]

Show the status of the submodules. This will print the SHA-1 of the currently checked out commit for each submodule, along with the submodule path and the output of git describe for the SHA-1. Each SHA-1 will be prefixed with - if the submodule is not initialized, + if the currently checked out submodule commit does not match the SHA-1 found in the index of the containing repository and U if the submodule has merge conflicts.

If --recursive is specified, this command will recurse into nested submodules, and show their status as well.

If you are only interested in changes of the currently initialized submodules with respect to the commit recorded in the index or the HEAD, linkgit:git-status[1] and linkgit:git-diff[1] will provide that information too (and can also report changes to a submodule’s work tree).

init [--] [<path>...]

Initialize the submodules recorded in the index (which were added and committed elsewhere) by setting submodule.$name.url in .git/config. It uses the same setting from .gitmodules as a template. If the URL is relative, it will be resolved using the default remote. If there is no default remote, the current repository will be assumed to be upstream.

Optional <path> arguments limit which submodules will be initialized. If no path is specified and submodule.active has been configured, submodules configured to be active will be initialized, otherwise all submodules are initialized.

When present, it will also copy the value of submodule.$name.update. This command does not alter existing information in .git/config. You can then customize the submodule clone URLs in .git/config for your local setup and proceed to git submodule update; you can also just use git submodule update --init without the explicit init step if you do not intend to customize any submodule locations.

See the add subcommand for the defintion of default remote.

deinit [-f|--force] (--all|[--] <path>...)

Unregister the given submodules, i.e. remove the whole submodule.$name section from .git/config together with their work tree. Further calls to git submodule update, git submodule foreach and git submodule sync will skip any unregistered submodules until they are initialized again, so use this command if you don’t want to have a local checkout of the submodule in your working tree anymore. If you really want to remove a submodule from the repository and commit that use linkgit:git-rm[1] instead.

When the command is run without pathspec, it errors out, instead of deinit-ing everything, to prevent mistakes.

If --force is specified, the submodule’s working tree will be removed even if it contains local modifications.

update [--init] [--remote] [-N|--no-fetch] [--[no-]recommend-shallow] [-f|--force] [--checkout|--rebase|--merge] [--reference <repository>] [--depth <depth>] [--recursive] [--jobs <n>] [--] [<path>...]

Update the registered submodules to match what the superproject expects by cloning missing submodules and updating the working tree of the submodules. The “updating” can be done in several ways depending on command line options and the value of submodule.<name>.update configuration variable. The command line option takes precedence over the configuration variable. if neither is given, a checkout is performed. update procedures supported both from the command line as well as setting submodule.<name>.update:

checkout

the commit recorded in the superproject will be checked out in the submodule on a detached HEAD.

If --force is specified, the submodule will be checked out (using git checkout --force if appropriate), even if the commit specified in the index of the containing repository already matches the commit checked out in the submodule.

rebase

the current branch of the submodule will be rebased onto the commit recorded in the superproject.

merge

the commit recorded in the superproject will be merged into the current branch in the submodule.

The following procedures are only available via the submodule.<name>.update configuration variable:

custom command

arbitrary shell command that takes a single argument (the sha1 of the commit recorded in the superproject) is executed. When submodule.<name>.update is set to !command, the remainder after the exclamation mark is the custom command.

none

the submodule is not updated.

If the submodule is not yet initialized, and you just want to use the setting as stored in .gitmodules, you can automatically initialize the submodule with the --init option.

If --recursive is specified, this command will recurse into the registered submodules, and update any nested submodules within.

summary [--cached|--files] [(-n|--summary-limit) <n>] [commit] [--] [<path>...]

Show commit summary between the given commit (defaults to HEAD) and working tree/index. For a submodule in question, a series of commits in the submodule between the given super project commit and the index or working tree (switched by --cached) are shown. If the option --files is given, show the series of commits in the submodule between the index of the super project and the working tree of the submodule (this option doesn’t allow to use the --cached option or to provide an explicit commit).

Using the --submodule=log option with linkgit:git-diff[1] will provide that information too.

foreach [--recursive] <command>

Evaluates an arbitrary shell command in each checked out submodule. The command has access to the variables $name, $path, $sha1 and $toplevel: $name is the name of the relevant submodule section in .gitmodules, $path is the name of the submodule directory relative to the superproject, $sha1 is the commit as recorded in the superproject, and $toplevel is the absolute path to the top-level of the superproject. Any submodules defined in the superproject but not checked out are ignored by this command. Unless given --quiet, foreach prints the name of each submodule before evaluating the command. If --recursive is given, submodules are traversed recursively (i.e. the given shell command is evaluated in nested submodules as well). A non-zero return from the command in any submodule causes the processing to terminate. This can be overridden by adding || : to the end of the command.

As an example, the command below will show the path and currently checked out commit for each submodule:

git submodule foreach 'echo $path `git rev-parse HEAD`'

sync [--recursive] [--] [<path>...]

Synchronizes submodules’ remote URL configuration setting to the value specified in .gitmodules. It will only affect those submodules which already have a URL entry in .git/config (that is the case when they are initialized or freshly added). This is useful when submodule URLs change upstream and you need to update your local repositories accordingly.

“git submodule sync” synchronizes all submodules while “git submodule sync – A” synchronizes submodule “A” only.

If --recursive is specified, this command will recurse into the registered submodules, and sync any nested submodules within.

absorbgitdirs

If a git directory of a submodule is inside the submodule, move the git directory of the submodule into its superprojects $GIT_DIR/modules path and then connect the git directory and its working directory by setting the core.worktree and adding a .git file pointing to the git directory embedded in the superprojects git directory.

A repository that was cloned independently and later added as a submodule or old setups have the submodules git directory inside the submodule instead of embedded into the superprojects git directory.

This command is recursive by default.

OPTIONS

-q; --quiet

Only print error messages.

--all

This option is only valid for the deinit command. Unregister all submodules in the working tree.

-b; --branch

Branch of repository to add as submodule. The name of the branch is recorded as submodule.<name>.branch in .gitmodules for update --remote. A special value of . is used to indicate that the name of the branch in the submodule should be the same name as the current branch in the current repository.

-f; --force

This option is only valid for add, deinit and update commands. When running add, allow adding an otherwise ignored submodule path. When running deinit the submodule working trees will be removed even if they contain local changes. When running update (only effective with the checkout procedure), throw away local changes in submodules when switching to a different commit; and always run a checkout operation in the submodule, even if the commit listed in the index of the containing repository matches the commit checked out in the submodule.

--cached

This option is only valid for status and summary commands. These commands typically use the commit found in the submodule HEAD, but with this option, the commit stored in the index is used instead.

--files

This option is only valid for the summary command. This command compares the commit in the index with that in the submodule HEAD when this option is used.

-n; --summary-limit

This option is only valid for the summary command. Limit the summary size (number of commits shown in total). Giving 0 will disable the summary; a negative number means unlimited (the default). This limit only applies to modified submodules. The size is always limited to 1 for added/deleted/typechanged submodules.

--remote

This option is only valid for the update command. Instead of using the superproject’s recorded SHA-1 to update the submodule, use the status of the submodule’s remote-tracking branch. The remote used is branch’s remote (branch.<name>.remote), defaulting to origin. The remote branch used defaults to master, but the branch name may be overridden by setting the submodule.<name>.branch option in either .gitmodules or .git/config (with .git/config taking precedence).

This works for any of the supported update procedures (--checkout, --rebase, etc.). The only change is the source of the target SHA-1. For example, submodule update --remote --merge will merge upstream submodule changes into the submodules, while submodule update --merge will merge superproject gitlink changes into the submodules.

In order to ensure a current tracking branch state, update --remote fetches the submodule’s remote repository before calculating the SHA-1. If you don’t want to fetch, you should use submodule update --remote --no-fetch.

Use this option to integrate changes from the upstream subproject with your submodule’s current HEAD. Alternatively, you can run git pull from the submodule, which is equivalent except for the remote branch name: update --remote uses the default upstream repository and submodule.<name>.branch, while git pull uses the submodule’s branch.<name>.merge. Prefer submodule.<name>.branch if you want to distribute the default upstream branch with the superproject and branch.<name>.merge if you want a more native feel while working in the submodule itself.

-N; --no-fetch

This option is only valid for the update command. Don’t fetch new objects from the remote site.

--checkout

This option is only valid for the update command. Checkout the commit recorded in the superproject on a detached HEAD in the submodule. This is the default behavior, the main use of this option is to override submodule.$name.update when set to a value other than checkout. If the key submodule.$name.update is either not explicitly set or set to checkout, this option is implicit.

--merge

This option is only valid for the update command. Merge the commit recorded in the superproject into the current branch of the submodule. If this option is given, the submodule’s HEAD will not be detached. If a merge failure prevents this process, you will have to resolve the resulting conflicts within the submodule with the usual conflict resolution tools. If the key submodule.$name.update is set to merge, this option is implicit.

--rebase

This option is only valid for the update command. Rebase the current branch onto the commit recorded in the superproject. If this option is given, the submodule’s HEAD will not be detached. If a merge failure prevents this process, you will have to resolve these failures with linkgit:git-rebase[1]. If the key submodule.$name.update is set to rebase, this option is implicit.

--init

This option is only valid for the update command. Initialize all submodules for which “git submodule init” has not been called so far before updating.

--name

This option is only valid for the add command. It sets the submodule’s name to the given string instead of defaulting to its path. The name must be valid as a directory name and may not end with a /.

--reference <repository>

This option is only valid for add and update commands. These commands sometimes need to clone a remote repository. In this case, this option will be passed to the linkgit:git-clone[1] command.

NOTE: Do not use this option unless you have read the note for linkgit:git-clone[1]’s --reference and --shared options carefully.

--recursive

This option is only valid for foreach, update, status and sync commands. Traverse submodules recursively. The operation is performed not only in the submodules of the current repo, but also in any nested submodules inside those submodules (and so on).

--depth

This option is valid for add and update commands. Create a shallow clone with a history truncated to the specified number of revisions. See linkgit:git-clone[1]

--[no-]recommend-shallow

This option is only valid for the update command. The initial clone of a submodule will use the recommended submodule.<name>.shallow as provided by the .gitmodules file by default. To ignore the suggestions use --no-recommend-shallow.

-j <n>; --jobs <n>

This option is only valid for the update command. Clone new submodules in parallel with as many jobs. Defaults to the submodule.fetchJobs option.

<path>...

Paths to submodule(s). When specified this will restrict the command to only operate on the submodules found at the specified paths. (This argument is required with add).

FILES

When initializing submodules, a .gitmodules file in the top-level directory of the containing repository is used to find the url of each submodule. This file should be formatted in the same way as $GIT_DIR/config. The key to each submodule url is “submodule.$name.url”. See linkgit:gitmodules[5] for details.

GIT

Part of the linkgit:git[1] suite