Branching a project
===================

Branch URLs
-----------

Before someone else can get a copy of your work, you need to
agree on a transfer technology.
You may decide to make the top level directory of your branch
a network share, an approach familiar to Windows users.
Unix users might prefer access to be
via SSH, a secure protocol built-in to most SSH servers.
Breezy is *very* flexible in this regard with support for
lots of protocols some of which are given below.

  ===========         ======================================================
  Prefix              Description
  ===========         ======================================================
  \file://            Access using the standard filesystem (default).
  \bzr+ssh:/          Access over SSH (best remote option).
  \sftp://            Access using SFTP (most SSH servers provide SFTP).
  \bzr://             Fast access using the Breezy smart server.
  \ftp://             Access using passive FTP.
  \http://            Access to branches exported by a web server.
  \https://           Encrypted access to branches exported by a web server.
  ===========         ======================================================

As indicated above, branches are identified using URLs with the
prefix indicating the transfer technology. If no prefix is given,
normal filenames are assumed. For a complete list of supported
protocols, see the ``urlspec`` online help topic or the
`URL Identifiers <../user-reference/index.html#url-identifiers>`_
section of the Breezy User Reference.

URLs are normally resolved relative to the root directory of the server,
so ``ftp://example.com/repo/foo`` means the ``/repo/foo`` directory of
that host.  (We say 'normally' because some server software like Apache
can be configured to remap URLs arbitrarily, in which case you'll need to
look at the server configuration to find out which URL corresponds to
which directory.)

To address a path relative to your home directory on the server, use a
tilde like so: ``bzr+ssh://example.com/~/public_html`` should map to
``public_html`` within your home directory.

.. note:: Access over HTTP or HTTPS is read-only by default.
   See `Pushing over the HTTP smart server
   <http_smart_server.html#pushing-over-the-http-smart-server>`_ for
   details on configuring read-write access.

A reminder about shared repositories
------------------------------------

Before getting a copy of a branch, have a quick think about
where to put it on your filesystem. For maximum storage
efficiency down the track, it is recommended that branches
be created somewhere under a directory that has been set up
as a shared repository. (See `Feature branches
<organizing_your_workspace.html#feature-branches>`_ in
`Organizing your workspace <organizing_your_workspace.html>`_
for a commonly used layout.) For example::

  brz init-shared-repo my-repo
  cd my-repo

You are now ready to grab a branch from someone else and
hack away.

The branch command
------------------

To get a branch based on an existing branch, use the ``branch`` command.
The syntax is::

  brz branch URL [directory]

If a directory is not given, one is created based on the last part of
the URL. Here are some examples showing a drive qualified path (M:/) and an
SFTP URL respectively::

  brz branch M:/cool-trunk
  brz branch sftp://bill@mary-laptop/cool-repo/cool-trunk

This example shows explicitly giving the directory name to use for the
new branch::

  brz branch /home/mary/cool-repo/cool-trunk cool

Time and space considerations
-----------------------------

Depending on the size of the branch being transferred and the
speed and latency of the network between your computer and the
source branch, this initial transfer might take some time.
Subsequent updates should be much faster as only the
changes are transferred then.

Keep in mind that Breezy is transferring the
complete history of the branch, not just the latest snapshot.
As a consequence, you can be off the network (or disconnected
from the network share) after ``branch`` completes but you'll
still be able to ``log`` and ``diff`` the history of the
branch as much as you want. Furthermore, these operations
are quick as the history is stored locally.

Note that Breezy uses smart compression technology to
minimize the amount of disk space required to store version
history. In many cases, the complete history of a project
will take up less disk space than the working copy of
the latest version.

As explained in later chapters, Breezy also has support for
`lightweight checkouts <using_checkouts.html#getting-a-lightweight-checkout>`_
of a branch, i.e. working trees with
no local storage of history. Of course, disconnected usage
is not available then but that's a tradeoff you can decide
to make if local disk space is really tight for you. Support for
limited lookback into history - *history horizons* - is
currently under development as well.

Viewing branch information
--------------------------

If you wish to see information about a branch including where it came from,
use the ``info`` command. For example::

  brz info cool

If no branch is given, information on the current branch is displayed.