~bzr-pqm/bzr/bzr.dev

=======================
Integrating with Bazaar
=======================

This document provides some general observations on integrating with
Bazaar and some recipes for typical tasks.  It is intended to be useful to
someone developing either a plugin or some other piece of software that
integrates with bzr.  If you want to know about a topic that's not covered
here, just ask us.




Starting with bzrlib
====================

Before doing anything else with bzrlib, you should run `bzrlib.initialize`
which sets up some global state.  


Running bzr commands
====================

To run command-line commands in-process::

  from bzrlib.commands import get_command
  
  cmd = get_command('version')
  cmd.run([])
  
This will send output through the current UIFactory; you can redirect this
elsewhere through the parameters to `bzrlib.initialize`.


Manipulating the Working Tree
=============================
Most objects in Bazaar are in files, named after the class they contain.
To manipulate the Working Tree we need a valid WorkingTree object, which
is loaded from the workingtree.py file, eg::

  from bzrlib import workingtree
  wt = workingtree.WorkingTree.open('/home/jebw/bzrtest')


This gives us a WorkingTree object, which has various methods spread over
itself, and its parent classes MutableTree and Tree - its worth having a
look through these three files (workingtree.py, mutabletree.py and tree.py)
to see which methods are available.

Compare trees
-------------

There are two methods for comparing trees: ``changes_from`` and
``iter_changes``.  ``iter_changes`` is more regular and precise, but it is
somewhat harder to work with.  See the API documentation for more details.

``changes_from`` creates a Delta object showing changes::

  from bzrlib import delta
  changes = wt.changes_from(wt.basis_tree())

This gives us a Delta object, which has several lists of files for each type of
change, eg changes.added is a list of added files, changes.removed is list
of removed files, changes.modified is a list of modified files. The contents
of the lists aren't just filenames, but include other information as well.
To grab just the filename we want the first value, eg::

  print("list of newly added files")
  for filename in changes.added:
    print("%s has been added" % filename[0])


The exception to this is changes.renamed, where the list returned for each
renamed files contains both the old and new names -- one or both may interest
you, depending on what you're doing.

For example::

  print("list of renamed files")
  for filename in changes.renamed:
    print("%s has been renamed to %s" % (filename[0], filename[1]))


Adding Files
------------

If you want to add files the same way ``bzr add`` does, you can use
MutableTree.smart_add.  By default, this is recursive. Paths can either be
absolute or relative to the workingtree::

  wt.smart_add(['dir1/filea.txt', 'fileb.txt',
                '/home/jebw/bzrtesttree/filec.txt'])


For more precise control over which files to add, use MutableTree.add::

  wt.add(['dir1/filea.txt', 'fileb.txt', '/home/jebw/bzrtesttree/filec.txt'])


Removing Files
--------------

You can remove multiple files at once.  The file paths need to be relative
to the workingtree::

  wt.remove(['filea.txt', 'fileb.txt', 'dir1'])


By default, the files are not deleted, just removed from the inventory.
To delete them from the filesystem as well::

  wt.remove(['filea.txt', 'fileb.txt', 'dir1'], keep_files=False)


Renaming a File
---------------

You can rename one file to a different name using WorkingTree.rename_one.
You just provide the old and new names, eg::

  wt.rename_one('oldfile.txt','newfile.txt')


Moving Files
------------

You can move multiple files from one directory into another using
WorkingTree.move::

  wt.move(['olddir/file.txt'], 'newdir')


More complicated renames/moves can be done with transform.TreeTransform,
which is outside the scope of this document.


Committing Changes
------------------

To commit _all_ the changes to our working tree we can just call the
WorkingTree's commit method, giving it a commit message, eg::

  wt.commit('this is my commit message')


To commit only certain files, we need to provide a list of filenames which we
want committing, eg::

  wt.commit(message='this is my commit message', specific_files=['fileA.txt',
            'dir2/fileB.txt', 'fileD.txt'])


Generating a Log for a File
===========================

Generating a log is, in itself, simple.  Grab a branch (see below) and pass
it to show_log together with a log formatter, eg::

  from bzrlib import log
  from bzrlib import branch

  b = branch.Branch.open('/path/to/bazaar/branch')
  lf = log.LongLogFormatter(to_file=sys.stdout)
  log.show_log(b, lf)


Three log formatters are included with bzrlib: LongLogFormatter,
ShortLogFormatter and LineLogFormatter.  These provide long, short and
single-line log output formats. It's also possible to write your own in
very little code.

Annotating a File
=================

To annotate a file, we want to walk every line of a file, retrieving the
revision which last modified/created that line and then retrieving the
information for that revision.

First we get an annotation iterator for the file we are interested in::

  tree, relpath = workingtree.WorkingTree.open_containing('/path/to/file.txt')
  fileid = tree.path2id(relpath)
  annotation = list(tree.annotate_iter(fileid))


To avoid repeatedly retrieving the same revisions we grab all revisions
associated with the file at once and build up a map of id to revision
information. We also build an map of revision numbers, again indexed
by the revision id::

  revision_ids = set(revision_id for revision_id, text in annotation)
  revisions = tree.branch.repository.get_revisions(revision_ids)
  revision_map = dict(izip(revision_ids, revisions))
  revno_map = tree.branch.get_revision_id_to_revno_map()


Finally, we use our annotation iterator to walk the lines of the file,
displaying the information from our revision maps as we go::

  for revision_id, text in annotation :
      rev = revision_map[revision_id]
      revno = revno_map[revision_id]
      revno_string = '.'.join(str(i) for i in revno)
      print "%s, %s: %s" % (revno_string, rev.committer, text)


Working with branches
=====================

To work with a branch you need a branch object, created from your branch::

  from bzrlib import branch

  b = branch.Branch.open('/home/jebw/bzrtest')


Branching from an existing branch
---------------------------------

To branch you create a branch object representing the branch you are
branching from, and supply a path/url to the new branch location.
The following code clones the bzr.dev branch (the latest copy of the Bazaar
source code) - be warned it has to download 60meg so takes a while to run
with no feedback::

  from bzrlib import branch

  b = branch.Branch.open('http://bazaar.launchpad.net/~bzr-pqm/bzr/bzr.dev')
  nb = b.bzrdir.sprout('/tmp/newBzrBranch').open_branch()


This provides no feedback, since Bazaar automatically uses the 'silent' UI.


Pushing and pulling branches
----------------------------

To push a branch you need to open the source and destination branches, then
just call push with the other branch as a parameter::

  from bzrlib import branch

  b1 = branch.Branch.open('file:///home/user/mybranch')
  b2 = branch.Branch.open('http://bazaar.launchpad.net/~bzr-pqm/bzr/bzr.dev')
  b1.push(b2)


Pulling is much the same::

  b1.pull(b2)


If you have a working tree, as well as a branch, you should use
WorkingTree.pull, not Branch.pull.

This won't handle conflicts automatically though, so any conflicts will be
left in the working tree for the user to resolve.


Checkout from an existing branch
================================

This performs a Lightweight checkout from an existing Branch::

  from bzrlib import bzrdir

  accelerator_tree, source = bzrdir.BzrDir.open_tree_or_branch('http:URL')
  source.create_checkout('/tmp/newBzrCheckout', None, True, accelerator_tree)


To make a heavyweight checkout, change the last line to::

  source.create_checkout('/tmp/newBzrCheckout', None, False, accelerator_tree


History Operations
==================

Finding the last revision number or id
--------------------------------------

To get the last revision number and id of a branch use::

  revision_number, revision_id = branch.last_revision_info()


If all you care about is the revision_id there is also the
method::

  revision_id = branch.last_revision()


Getting the list of revision ids that make up a branch
------------------------------------------------------

IMPORTANT: This should be avoided wherever possible, as it scales with the
length of history::

  revisions = branch.revision_history()

now revisions[0] is the revision id of the first commit, and revs[-1] is the
revision id of the most recent. Note that if all you want is the last
revision then you should use branch.last_revision() as described above, as
it is vastly more efficient.


Getting a Revision object from a revision id
--------------------------------------------

The Revision object has attributes like "message" to get the information
about the revision::

  repo = branch.repository
  revision = repo.get_revision(rev_id)


Accessing the files from a revision
-----------------------------------

To get the file contents and tree shape for a specific revision you need
a RevisionTree. These are supplied by the repository for a specific
revision id::

  revtree = repo.revision_tree(rev_id)

RevisionTrees, like all trees, can be compared as described in "Comparing
Trees" above.

The most common way to list files in a tree is ``Tree.iter_entries()``.
The simplest way to get file content is ``Tree.get_file()``.  The best way
to retrieve file content for large numbers of files `Tree.iter_files_bytes()``