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.. This file is in Python ReStructuredText format - it can be formatted
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.. into HTML or text. In the future we plan to extract the example commands
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.. and automatically test them.
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.. This text was previously on the wiki at
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.. http://bazaar.canonical.com/IntroductionToBzr
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.. but has been moved into the source tree so it can be kept in sync with
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.. the source and possibly automatically checked.
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Current for bzr-0.8, 2006-04
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If you are already familiar with decentralized revision control, then
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please feel free to skip ahead to "Introducing Yourself to Bazaar-NG". If,
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on the other hand, you are familiar with revision control but not
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decentralized revision control, then please start at "How DRCS is
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different." Otherwise, get some coffee or tea, get comfortable and get
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The Purposes of Revision Control
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================================
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Odds are that you have worked on some sort of textual data -- the sources
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to a program, web sites or the config files that Unix system
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administrators have to deal with in /etc. The chances are also good that
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you have made some sort of mistake that you deeply regretted. Perhaps you
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deleted the configuration file for your mailserver or perhaps mauled the
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source code for a pet project. Whatever happened, you have just deleted
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important information that you would desperately like to get back. If this
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has ever happened to you, then you are probably ready for Bazaar-NG.
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Revision control systems (which I'll henceforth call RCS) such as
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Bazaar-NG give you the ability to track changes for a directory by turning
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it into something slightly more complicated than a directory that we call
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a **branch**. The branch not only stores how the directory looks right
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now, but also how it looked at various points in the past. Then, when you
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do something you wish you hadn't, you can restore the directory to the way
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it looked at some point in the past.
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Revision control systems give users the ability to save changes to a
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branch by "committing a **revision**". The revision created is essentially
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a summary of the changes that were made since the last time the tree was
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These revisions have other uses as well. For example, one can comment
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revisions to record what the recent set of changes meant by providing an
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optional log message. Real life log messages include things like "Fixed
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the web template to close the table" and "Added sftp suppport. Fixes #595"
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We keep these logs so that if later there is some sort of problem with
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sftp, we can figure out when the problem probably happened.
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Many Revision Control Systems (RCS) are stored on servers. If one wants to
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work on the code stored within an RCS, then one needs to connect to the
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server and "checkout" the code. Doing so gives one a directory in which a
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person can make changes and then commit. The RCS client then connects to
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the RCS server and stores the changes. This method is known as the
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The centralized model can have some drawbacks. A centralized RCS requires
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that one is able to connect to the server whenever one wants to do version
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control work. This can be a bit of a problem if your server on some other
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machine on the internet and you are not. Or, worse yet, you ''are'' on the
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internet but the server is missing!
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Decentralized Revision Control Systems (which I'll call DRCS after this
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point) deal with this problem by keeping branches on the same machine as
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the client. In Bazaar-NG's case, the branch is kept in the same place as
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the code that is being version controlled. This allows the user to save
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his changes (**commit**) whenever he wants -- even if he is offline. The
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user only needs internet access when he wants to access the changes in
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someone else's branch that are somewhere else.
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A common requirement that many people have is the need to keep track of
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the changes for a directory such as file and subdirectory changes.
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Performing this tracking by hand is a awkward process that over time
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becomes unwieldy. That is, until one considers version control tools such
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as Bazaar-NG. These tools automate the process of storing data by creating
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a **revision** of the directory tree whenever the user asks.
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Revision control software such as Bazaar-NG can do much more than just
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storage and performing undo. For example, with Bazaar-NG developer can
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take the modifications in one branch of software and apply them to
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another, related, branch -- even if those changes exist in a branch owned
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by somebody else. This allows developers to cooperate without giving write
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Bazaar-NG remembers the ''ancestry'' of a revision: the previous revisions
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that it is based upon. A single revision may have more than one direct
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descendant, each with different changes, representing a divergence in the
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evolution of the tree. By branching, Bazaar-NG allows multiple people to
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cooperate on the evolution of a project, without all needing to work in
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strict lock-step. Branching can be useful even for a single developer.
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Introducing yourself to Bazaar-NG
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=================================
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Bazaar-NG installs a single new command, **bzr**. Everything else is a
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subcommand of this. You can get some help with `bzr help`. There will be
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One function of a version control system is to keep track of who changed
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what. In a decentralized system, that requires an identifier for each
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author that is globally unique. Most people already have one of these: an
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email address. Bzr is smart enough to automatically generate an email
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address by looking up your username and hostname. If you don't like the
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guess that Bazaar-NG makes, then three options exist:
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1. Setting the email address in the
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``~/.bazaar/bazaar.conf`` by adding the following lines. Please note that
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``[DEFAULT]`` is case sensitive::
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email= Your Name <email@isp.com>
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1. Override the previous setting on a
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branch by branch basis by creating a branch section in
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``~/.bazaar/branches.conf`` by adding the following lines::
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[/the/directory/to/the/branch]
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email=Your Name <email@isp.com>
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1. Overriding the two previous options by setting the global environment
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variable ``$BZREMAIL`` or ``$EMAIL`` (``$BZREMAIL`` will take precedence)
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to your full email address.
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History is by default stored in the .bzr directory of the branch. There
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will be a facility to store it in a separate repository, which may be
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remote. We create a new branch by running **bzr init** in an existing
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/home/mbp/work/bzr.test/tutorial
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As for CVS, there are three classes of file: unknown, ignored, and
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versioned. The **add** command makes a file versioned: that is, changes
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to it will be recorded by the system::
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% echo 'hello world' > hello.txt
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If you add the wrong file, simply use **bzr remove** to make it
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unversioned again. This does not delete the working copy.
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All history is stored in a branch, which is just an on-disk directory
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containing control files. By default there is no separate repository or
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database as used in svn or svk. You can choose to create a repository if
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you want to (see the **bzr init-repo** command). You may wish to do this
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if you have very large branches, or many branches of a moderate sized
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You'll usually refer to branches on your computer's filesystem just by
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giving the name of the directory containing the branch. bzr also supports
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accessing branches over http, for example::
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% bzr log http://bazaar-ng.org/bzr/bzr.dev/
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By installing bzr plugins you can also access branches over the sftp or
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Once you have completed some work, you will want to **commit** it to the
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version history. It is good to commit fairly often: whenever you get a
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new feature working, fix a bug, or improve some code or documentation.
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It's also a good practice to make sure that the code compiles and passes
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its test suite before committing, to make sure that every revision is a
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known-good state. You can also review your changes, to make sure you're
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committing what you intend to, and as a chance to rethink your work before
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you permanently record it.
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Two bzr commands are particularly useful here: **status** and **diff**.
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The **status** command tells you what changes have been made to the
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working directory since the last revision::
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By default **bzr status** hides "boring" files that are either unchanged
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or ignored. To see them too, use the --all option. The status command
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can optionally be given the name of some files or directories to check.
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The **diff** command shows the full text of changes to all files as a
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standard unified diff. This can be piped through many programs such as
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''patch'', ''diffstat'', ''filterdiff'' and ''colordiff''::
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*** added file 'hello.txt'
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With the ''-r'' option, the tree is compared to an earlier revision, or
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the differences between two versions are shown::
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% bzr diff -r 1000.. # everything since r1000
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% bzr diff -r 1000..1100 # changes from 1000 to 1100
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The --diff-options option causes bzr to run the external diff program,
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passing options. For example::
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% bzr diff --diff-options --side-by-side foo
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When the working tree state is satisfactory, it can be **committed** to
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the branch, creating a new revision holding a snapshot of that state.
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The **commit** command takes a message describing the changes in the
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revision. It also records your userid, the current time and timezone, and
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the inventory and contents of the tree. The commit message is specified
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by the ''-m'' or ''--message'' option. You can enter a multi-line commit
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message; in most shells you can enter this just by leaving the quotes open
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at the end of the line.
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% bzr commit -m "added my first file"
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You can also use the -F option to take the message from a file. Some
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people like to make notes for a commit message while they work, then
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review the diff to make sure they did what they said they did. (This file
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can also be useful when you pick up your work after a break.)
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Message from an editor
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======================
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If you use neither the `-m` nor the `-F` option then bzr will open an
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editor for you to enter a message. The editor to run is controlled by
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your `$EDITOR` environment variable or
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add `editor` to ~/.bazaar/bazaar.conf; `$BZR_EDITOR` will override
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the above mentioned editor options. If you quit the editor without
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making any changes, the commit will be cancelled.
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If you give file or directory names on the commit command line then only
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the changes to those files will be committed. For example::
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% bzr commit -m "documentation fix" commit.py
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By default bzr always commits all changes to the tree, even if run from a
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subdirectory. To commit from only the current directory down, use::
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Removing uncommitted changes
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============================
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If you've made some changes and don't want to keep them, use the
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**revert** command to go back to the previous head version. It's a good
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idea to use **bzr diff** first to see what will be removed. By default the
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revert command reverts the whole tree; if file or directory names are
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given then only those ones will be affected. **revert** also clears the
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list of pending merges revisions.
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Many source trees contain some files that do not need to be versioned,
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such as editor backups, object or bytecode files, and built programs. You
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can simply not add them, but then they'll always crop up as unknown files.
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You can also tell bzr to ignore these files by adding them to a file
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called ''.bzrignore'' at the top of the tree.
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This file contains a list of file wildcards (or "globs"), one per line.
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Typical contents are like this::
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If a glob contains a slash, it is matched against the whole path from the
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top of the tree; otherwise it is matched against only the filename. So
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the previous example ignores files with extension ``.o`` in all
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subdirectories, but this example ignores only config.h at the top level
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and HTML files in ``doc/``::
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To get a list of which files are ignored and what pattern they matched,
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use ''bzr ignored''::
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It is OK to have either an ignore pattern match a versioned file, or to
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add an ignored file. Ignore patterns have no effect on versioned files;
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they only determine whether unversioned files are reported as unknown or
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The ''.bzrignore'' file should normally be versioned, so that new copies
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of the branch see the same patterns::
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% bzr commit -m "Add ignore patterns"
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The **bzr log** command shows a list of previous revisions. The **bzr log
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--forward** command does the same in chronological order to get most
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recent revisions printed at last.
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As with bzr diff, bzr log supports the -r argument::
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% bzr log -r 1000.. # Revision 1000 and everything after it
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% bzr log -r ..1000 # Everything up to and including r1000
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% bzr log -r 1000..1100 # changes from 1000 to 1100
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% bzr log -r 1000 # The changes in only revision 1000
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The **bzr info** command shows some summary information about the working
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tree and the branch history.
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Versioning directories
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======================
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bzr versions files and directories in a way that can keep track of renames
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and intelligently merge them::
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% echo 'int main() {}' > src/simple.c
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% bzr add src/simple.c
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Deleting and removing files
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===========================
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You can delete files or directories by just deleting them from the working
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directory. This is a bit different to CVS, which requires that you also
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**bzr remove** makes the file un-versioned, but does not delete
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the working copy. This is useful when you add the wrong file, or decide
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that a file should actually not be versioned.
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% bzr remove -v hello.txt
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If you remove the wrong file by accident, you can use **bzr revert** to
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Often rather than starting your own project, you will want to submit a
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change to an existing project. You can get a copy of an existing branch
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by copying its directory, expanding a tarball, or by a remote copy using
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something like rsync. You can also use bzr to fetch a copy. Because this
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new copy is potentially a new branch, the command is called *branch*::
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% bzr branch http://bazaar-ng.org/bzr/bzr.dev
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This copies down the complete history of this branch, so we can do all
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operations on it locally: log, annotate, making and merging branches.
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There will be an option to get only part of the history if you wish.
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Following upstream changes
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==========================
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You can stay up-to-date with the parent branch by "pulling" in their
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After this change, the local directory will be a mirror of the source. This
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includes the ''revision-history'' - which is a list of the commits done in
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this branch, rather than merged from other branches.
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This command only works if your local (destination) branch is either an
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older copy of the parent branch with no new commits of its own, or if the
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most recent commit in your local branch has been merged into the parent
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Merging from related branches
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=============================
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If two branches have diverged (both have unique changes) then **bzr
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merge** is the appropriate command to use. Merge will automatically
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calculate the changes that exist in the branch you're merging from that
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are not in your branch and attempt to apply them in your branch.
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If there is a conflict during a merge, 3 files with the same basename are
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created. The filename of the common base is appended with .BASE, the
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filename of the file containing your changes is appended .THIS and the
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filename with the changes from the other tree is appended .OTHER.
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Using a program such as kdiff3, you can now comfortably merge them into
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one file. To commit you have to rename it to the original basename and
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delete the other two files. As long as there exist files with .BASE, .THIS
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or .OTHER the commit command will complain.
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[**TODO**: explain conflict markers within files]
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Publishing your branch
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======================
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You don't need a special server to publish a bzr branch, just a normal web
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server. Just mirror the files to your server, including the .bzr
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directory. One can push a branch (or the changes for a branch) by one of
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the following three methods:
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* Rsync: rsync -avrz LOCALBRANCH servername.com/this/directory/here
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(or any other tool for publishing a directory to a web site.)
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* bzr push sftp://servername.com/this/directory/here
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(The directory that must already exist)
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* The push plugin that comes with BzrTools
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removed
tutorial.txt
