Subrepositories let you nest external repositories or projects into a

parent Mercurial repository, and make commands operate on them as a

group.

Mercurial currently supports Mercurial, Git, and Subversion

subrepositories.

Subrepositories are made of three components:

1. Nested repository checkouts. They can appear anywhere in the

   parent working directory.

2. Nested repository references. They are defined in ``.hgsub`` and

   tell where the subrepository checkouts come from. Mercurial

   subrepositories are referenced like:

     path/to/nested = https://example.com/nested/repo/path

   Git and Subversion subrepos are also supported:

     path/to/nested = [git]git://example.com/nested/repo/path

     path/to/nested = [svn]https://example.com/nested/trunk/path

   where ``path/to/nested`` is the checkout location relatively to the

   parent Mercurial root, and ``https://example.com/nested/repo/path``

   is the source repository path. The source can also reference a

   filesystem path.

   Note that ``.hgsub`` does not exist by default in Mercurial

   repositories, you have to create and add it to the parent

   repository before using subrepositories.

3. Nested repository states. They are defined in ``.hgsubstate`` and

   capture whatever information is required to restore the

   subrepositories to the state they were committed in a parent

   repository changeset. Mercurial automatically record the nested

   repositories states when committing in the parent repository.

   .. note::

      The ``.hgsubstate`` file should not be edited manually.

Adding a Subrepository

----------------------

If ``.hgsub`` does not exist, create it and add it to the parent

repository. Clone or checkout the external projects where you want it

to live in the parent repository. Edit ``.hgsub`` and add the

subrepository entry as described above. At this point, the

subrepository is tracked and the next commit will record its state in

``.hgsubstate`` and bind it to the committed changeset.

Synchronizing a Subrepository

-----------------------------

Subrepos do not automatically track the latest changeset of their

sources. Instead, they are updated to the changeset that corresponds

with the changeset checked out in the top-level changeset. This is so

developers always get a consistent set of compatible code and

libraries when they update.

Thus, updating subrepos is a manual process. Simply check out target

subrepo at the desired revision, test in the top-level repo, then

commit in the parent repository to record the new combination.

Deleting a Subrepository

------------------------

To remove a subrepository from the parent repository, delete its

reference from ``.hgsub``, then remove its files.

Interaction with Mercurial Commands

-----------------------------------

:add: add does not recurse in subrepos unless -S/--subrepos is

    specified. Subversion subrepositories are currently silently

    ignored.

:archive: archive does not recurse in subrepositories unless

    -S/--subrepos is specified.

:commit: commit creates a consistent snapshot of the state of the

:diff: diff does not recurse in subrepos unless -S/--subrepos is

    specified. Changes are displayed as usual, on the subrepositories

    elements. Subversion subrepositories are currently silently

    ignored.

:incoming: incoming does not recurse in subrepos unless -S/--subrepos

    is specified. Subversion subrepositories are currently silently

    ignored.

:outgoing: outgoing does not recurse in subrepos unless -S/--subrepos

    is specified. Subversion subrepositories are currently silently

    ignored.

:pull: pull is not recursive since it is not clear what to pull prior

    to running :hg:`update`. Listing and retrieving all

    subrepositories changes referenced by the parent repository pulled

    changesets is expensive at best, impossible in the Subversion

    case.

:push: Mercurial will automatically push all subrepositories first

    when the parent repository is being pushed. This ensures new

    subrepository changes are available when referenced by top-level

    repositories.

:status: status does not recurse into subrepositories unless

    -S/--subrepos is specified. Subrepository changes are displayed as

    regular Mercurial changes on the subrepository

    elements. Subversion subrepositories are currently silently

    ignored.

:update: update restores the subrepos in the state they were

    originally committed in target changeset. If the recorded

    changeset is not available in the current subrepository, Mercurial

    will pull it in first before updating.  This means that updating

    can require network access when using subrepositories.

Remapping Subrepositories Sources

---------------------------------

A subrepository source location may change during a project life,

invalidating references stored in the parent repository history. To

fix this, rewriting rules can be defined in parent repository ``hgrc``

file or in Mercurial configuration. See the ``[subpaths]`` section in

hgrc(5) for more details.