Subrepositories

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", which should be placed in the root of working directory, 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", which is placed in the root of working directory, 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. However, if you specify the full path of a file in a subrepo, it will be added even without -S/--subrepos specified. Git and 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 entire project and its subrepositories. If any subrepositories have been modified, Mercurial will abort. Mercurial can be made to instead commit all modified subrepositories by specifying -S/--subrepos, or setting "ui.commitsubrepos=True" in a configuration file (see "hg help config"). After there are no longer any modified subrepositories, it records their state and finally commits it in the parent repository.

diff

diff does not recurse in subrepos unless -S/--subrepos is specified. Changes are displayed as usual, on the subrepositories elements. Git and Subversion subrepositories are currently silently ignored.

forget

forget currently only handles exact file matches in subrepos. Git and Subversion subrepositories are currently silently ignored.

incoming

incoming does not recurse in subrepos unless -S/--subrepos is specified. Git and Subversion subrepositories are currently silently ignored.

outgoing

outgoing does not recurse in subrepos unless -S/--subrepos is specified. Git and 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. Push is a no-op for Subversion subrepositories.

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.