git-submodule - Initialize, update or inspect submodules
Submodules allow foreign repositories to be embedded within a dedicated subdirectory of the source tree, always pointed at a particular commit.
They are not to be confused with remotes, which are meant mainly for branches 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.
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 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).
This command will manage the tree entries and contents of the gitmodules file for you, as well as inspect the status of your submodules and update them. When adding a new submodule to the tree, the add subcommand is to be used. However, when pulling a tree containing submodules, 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. You can briefly inspect the up-to-date status of your submodules using the status subcommand and get a detailed overview of the difference between the index and checkouts using the summary subcommand.
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 two arguments: <repository> and <path>.
<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 origin repository.
<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 need be provided: git-submodule will correctly locate the submodule using the relative URL in .gitmodules.
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 and + if the currently checked out submodule commit does not match the SHA-1 found in the index of the containing repository. This command is the default command for git-submodule.
Initialize the submodules, i.e. register each submodule name and url found in .gitmodules into .git/config. The key used in .git/config is submodule.$name.url. 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.
Update the registered submodules, i.e. clone missing submodules and checkout the commit specified in the index of the containing repository. This will make the submodules HEAD be detached.
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.
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.
Only print error messages.
Branch of repository to add as submodule.
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.
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.
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).
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 for details.
Written by Lars Hjemli <firstname.lastname@example.org>
Part of the linkgit:git suite