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如果您业已熟悉分散式版本修订控制(decentralized revision control),

The Purposes of Revision Control

如果您业已熟悉分散式版本修订控制(decentralized revision control),那么完全可以
放心大胆的直接跳到“了解 Bazaar-NG“一节。另外,如果您只是熟悉版本修订控制而非分散式版本

The Purposes of Revision Control 版本修订控制的目的
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How DRCS is Different How DRCS is Different DRCS有何不同
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Introducing yourself to Bazaar-NG 了解 Bazaar-NG

~- (!) 参考自: {en} ["IntroductionToBzr"]-~

Bazaar-NG 指南

Current for bzr-0.8, 2006-04 (from repository: doc/tutorial.txt)


If you are already familiar with decentralized revision control, then please feel free to skip ahead to "Introducing Yourself to Bazaar-NG". If, on the other hand, you are familiar with revision control but not decentralized revision control, then please start at "How DRCS is different." Otherwise, get some coffee or tea, get comfortable and get ready to catch up.

如果您业已熟悉分散式版本修订控制(decentralized revision control),那么完全可以 放心大胆的直接跳到“了解 Bazaar-NG“一节。另外,如果您只是熟悉版本修订控制而非分散式版本 修订控制,那么请从”DRCS有何不同“一节开始。否则,最好弄点咖啡或绿茶,调整状态,准备迎头 赶上吧。

The Purposes of Revision Control 版本修订控制的目的

System Message: WARNING/2 (<string>, line 36)

Title underline too short.

The Purposes of Revision Control 版本修订控制的目的

Odds are that you have worked on some sort of textual data -- the sources to a program, web sites or the config files that Unix system administrators have to deal with in /etc. The chances are also good that you have made some sort of mistake that you deeply regretted. Perhaps you deleted the configuration file for your mailserver or perhaps mauled the source code for a pet project. Whatever happened, you have just deleted important information that you would desperately like to get back. If this has ever happened to you, then you are probably ready for Bazaar-NG.

Revision control systems (which I'll henceforth call RCS) such as Bazaar-NG give you the ability to track changes for a directory by turning it into something slightly more complicated than a directory that we call a branch. The branch not only stores how the directory looks right now, but also how it looked at various points in the past. Then, when you do something you wish you hadn't, you can restore the directory to the way it looked at some point in the past.

Revision control systems give users the ability to save changes to a branch by "committing a revision". The revision created is essentially a summary of the changes that were made since the last time the tree was saved.

These revisions have other uses as well. For example, one can comment revisions to record what the recent set of changes meant by providing an optional log message. Real life log messages include things like "Fixed the web template to close the table" and "Added sftp support. Fixes #595"

We keep these logs so that if later there is some sort of problem with sftp, we can figure out when the problem probably happened.

How DRCS is Different DRCS有何不同

System Message: WARNING/2 (<string>, line 69)

Title underline too short.

How DRCS is Different DRCS有何不同

Many Revision Control Systems (RCS) are stored on servers. If one wants to work on the code stored within an RCS, then one needs to connect to the server and "checkout" the code. Doing so gives one a directory in which a person can make changes and then commit. The RCS client then connects to the RCS server and stores the changes. This method is known as the centralized model.

The centralized model can have some drawbacks. A centralized RCS requires that one is able to connect to the server whenever one wants to do version control work. This can be a bit of a problem if your server on some other machine on the internet and you are not. Or, worse yet, you ''are'' on the internet but the server is missing!

Decentralized Revision Control Systems (which I'll call DRCS after this point) deal with this problem by keeping branches on the same machine as the client. In Bazaar-NG's case, the branch is kept in the same place as the code that is being version controlled. This allows the user to save his changes (commit) whenever he wants -- even if he is offline. The user only needs internet access when he wants to access the changes in someone else's branch that are somewhere else.

A common requirement that many people have is the need to keep track of the changes for a directory such as file and subdirectory changes. Performing this tracking by hand is a awkward process that over time becomes unwieldy. That is, until one considers version control tools such as Bazaar-NG. These tools automate the process of storing data by creating a revision of the directory tree whenever the user asks.

Revision control software such as Bazaar-NG can do much more than just storage and performing undo. For example, with Bazaar-NG developer can take the modifications in one branch of software and apply them to another, related, branch -- even if those changes exist in a branch owned by somebody else. This allows developers to cooperate without giving write access to repository.

Bazaar-NG remembers the ''ancestry'' of a revision: the previous revisions that it is based upon. A single revision may have more than one direct descendant, each with different changes, representing a divergence in the evolution of the tree. By branching, Bazaar-NG allows multiple people to cooperate on the evolution of a project, without all needing to work in strict lock-step. Branching can be useful even for a single developer.

了解 Bazaar-NG

Bazaar-NG installs a single new command, bzr. Everything else is a subcommand of this. You can get some help with bzr help. There will be more in the future.

One function of a version control system is to keep track of who changed what. In a decentralized system, that requires an identifier for each author that is globally unique. Most people already have one of these: an email address. Bzr is smart enough to automatically generate an email address by looking up your username and hostname. If you don't like the guess that Bazaar-NG makes, then three options exist:

1. Setting the email address in the ~/.bazaar/bazaar.conf by adding the following lines. Please note that [DEFAULT] is case sensitive:

email= Your Name <>

1. Override the previous setting on a branch by branch basis by creating a branch section in ~/.bazaar/branches.conf by adding the following lines:

email=Your Name <>

1. Overriding the two previous options by setting the global environment variable $BZREMAIL or $EMAIL ($BZREMAIL will take precedence) to your full email address.

Creating a branch

History is by default stored in the .bzr directory of the branch. There will be a facility to store it in a separate repository, which may be remote. We create a new branch by running bzr init in an existing directory:

% mkdir tutorial
% cd tutorial
% ls -a
./  ../
% pwd
% bzr init
% ls -aF
./  ../  .bzr/

As for CVS, there are three classes of file: unknown, ignored, and versioned. The add command makes a file versioned: that is, changes to it will be recorded by the system:

% echo 'hello world' > hello.txt
% bzr status
% bzr unknowns
% bzr add hello.txt
added hello.txt
% bzr unknowns

If you add the wrong file, simply use bzr remove to make it unversioned again. This does not delete the working copy.

Branch locations

All history is stored in a branch, which is just an on-disk directory containing control files. By default there is no separate repository or database as used in svn or svk. You can choose to create a repository if you want to (see the bzr init-repo command). You may wish to do this if you have very large branches, or many branches of a moderate sized project.

You'll usually refer to branches on your computer's filesystem just by giving the name of the directory containing the branch. bzr also supports accessing branches over http, for example:

% bzr log

By installing bzr plugins you can also access branches over the sftp or rsync protocols.

Reviewing changes

Once you have completed some work, you will want to commit it to the version history. It is good to commit fairly often: whenever you get a new feature working, fix a bug, or improve some code or documentation. It's also a good practice to make sure that the code compiles and passes its test suite before committing, to make sure that every revision is a known-good state. You can also review your changes, to make sure you're committing what you intend to, and as a chance to rethink your work before you permanently record it.

Two bzr commands are particularly useful here: status and diff.

bzr status

The status command tells you what changes have been made to the working directory since the last revision:

% bzr status

By default bzr status hides "boring" files that are either unchanged or ignored. To see them too, use the --all option. The status command can optionally be given the name of some files or directories to check.

bzr diff

The diff command shows the full text of changes to all files as a standard unified diff. This can be piped through many programs such as ''patch'', ''diffstat'', ''filterdiff'' and ''colordiff'':

% bzr diff
*** added file 'hello.txt'
--- /dev/null
+++ hello.txt
@@ -1,0 +1,1 @@
+hello world

With the ''-r'' option, the tree is compared to an earlier revision, or the differences between two versions are shown:

% bzr diff -r 1000..          # everything since r1000
% bzr diff -r 1000..1100      # changes from 1000 to 1100

The --diff-options option causes bzr to run the external diff program, passing options. For example:

% bzr diff --diff-options --side-by-side foo

Some projects prefer patches to show a prefix at the start of the path for old and new files. The --prefix option can be used to provide such a prefix. As a shortcut, bzr diff -p1 produces a form that works with the command patch -p1.

Committing changes

When the working tree state is satisfactory, it can be committed to the branch, creating a new revision holding a snapshot of that state.

bzr commit

The commit command takes a message describing the changes in the revision. It also records your userid, the current time and timezone, and the inventory and contents of the tree. The commit message is specified by the ''-m'' or ''--message'' option. You can enter a multi-line commit message; in most shells you can enter this just by leaving the quotes open at the end of the line.

% bzr commit -m "added my first file"

You can also use the -F option to take the message from a file. Some people like to make notes for a commit message while they work, then review the diff to make sure they did what they said they did. (This file can also be useful when you pick up your work after a break.)

Message from an editor

If you use neither the -m nor the -F option then bzr will open an editor for you to enter a message. The editor to run is controlled by your $EDITOR environment variable or add editor to ~/.bazaar/bazaar.conf; $BZR_EDITOR will override the above mentioned editor options. If you quit the editor without making any changes, the commit will be cancelled.

Selective commit

If you give file or directory names on the commit command line then only the changes to those files will be committed. For example:

% bzr commit -m "documentation fix"

By default bzr always commits all changes to the tree, even if run from a subdirectory. To commit from only the current directory down, use:

% bzr commit .

Removing uncommitted changes

If you've made some changes and don't want to keep them, use the revert command to go back to the previous head version. It's a good idea to use bzr diff first to see what w