Difference between revisions of "Bzr Intro"

Latest revision as of 13:35, 31 July 2010

This class is not currently offered. Laurel 21:35, 31 July 2010 (UTC)

The Bzr Intro class should give a basic understanding of how to use the bzr revision control system and some of the useful helper utilities available for bzr.

background

prerequisites

basic familiarity with commandline and Command Line 2
familiarity with a text editor
access to a functional computer with `apt-get install bazaar`

suggested background

basic understanding of cvs, subversion or other revision control systems

topics covered

help

short help message:

bzr help

get a list and short description of all commands:

bzr help commands

get help on COMMAND:

bzr help COMMAND
bzr COMMAND -h

many commands have a short and long alias, help or -h will list them.

who am i

the first time you start working with bzr on a given machine, let it know who you are, so commit messages will have useful identifiers:

bzr whoami 'FOO BAR <FOO@example.com>'

starting a new project

bzr init PROJECT
cd PROJECT
bzr add FOO BAR BAZ
bzr ci -m 'added initial files'
bzr push --remember sftp://some.server/home/USERNAME/public_html/bzr/PROJECT/my-branch

working on an existing project

bzr get URL ORIGIN
bzr get ORIGIN NEW_FEATURE
cd NEW_FEATURE
while feature_is_incomplete:
   hack, tweak, etc.
   bzr di
   bzr ci
bzr push --remember sftp://some.server/home/USERNAME/public_html/bzr/PROJECT/NEW_FEATURE

announce that your branch has this cool new feature to the project mailing list or irc channel:

hey, just implemented a fix for bug #10: 
bzr get http://some.server/~USERNAME/bzr/PROJECT/NEW_FEATURE

staying in sync

after making lots of changes, and upstream made lots of changes, it's time to get back in sync with upstream:

bzr merge ../NEW_FEATURE
bzr ci -m 'merged amazing new feature: NEW_FEATURE'
bzr push sftp://some.server/home/USERNAME/public_html/bzr/PROJECT/my-branch

comparing revision history

get revision number of current branch:

bzr revno

get a log of revisions in current branch:

bzr log
bzr log --short

get log of revision 5:

bzr log -r 5

get a short log of revisions between 5 and 9:

bzr log -r 5..9 --short

get log of the last two revisions:

bzr log -r -2..

compare revisions between OTHER_BRANCH and current branch:

bzr missing OTHER_BRANCH 
bzr missing --short OTHER_BRANCH

partial merging

merge everything up to and including revision 5:

bzr merge -r 5 SOME_BRANCH

merge changes introduced in revision 6, but not revisions 1-5:

bzr merge -r 5..6 SOME_BRANCH

checkouts

checkouts are very similar to branches, with one key difference- by default, they require access to the original branch in order to commit.

bzr co ORIGIN LOCAL_CHECKOUT
cd LOCAL_CHECKOUT
date > test
bzr add test

make the ORIGIN branch inaccessible:

mv ../ORIGIN ../ORIGIN.borked

and then attempt a commit:

bzr ci

shared branches

multiple users can commit to the same branch, making sure everyone has read and write permission to the branch directory.

it is recommended to use the --append-revisions-only flag when creating the branch:

bzr init --append-revisions-only /path/to/shared/repository

otherwise, pushes and pulls can change the revision history, which makes it harder to keep track of who changed what when.

using checkouts in combination with shared branches, you get behavior very similar to a centralized VCS, such as subversion.

optimization

to use a common storage space for all your revisions:

bzr init-repo PROJECT

any branches checked out under PROJECT will share revision information when possible.

bzr get URL1 PROJECT/FOO
bzr get URL2 PROJECT/BAR

when you get the second branch, most of BAR is identical to FOO, so you only need to download the differences. highly recommended for publicly accessible branches.

tagging

in older versions, tagging was done merely by copying a branch to another location. this if you use the init-repo method to store your branches, this shares common revisions with other branches, so doesn't waste much space:

bzr push sftp://some.server/home/USERNAME/public_html/bzr/PROJECT/releases/FOO-1.2.3

with newer versions of bzr, you can use tags much like with cvs. it does require initializing the repository with a special format:

bzr init --dirstate-tags some-branch

if you forgot to do so, you can upgrade:

bzr upgrade --dirstate-tags .

then you can start making tags:

bzr tag SOME_TAG_NAME

tag revision 559 as with tag 1.2.3:

bzr tag -r 559 1.2.3

make a new branch from the tag 1.2.3:

bzr get -r tag:1.2.3 some-branch some-other-branch

related tools

converting an existing project from subversion or other vcs

with bzr-svn, it's rather simple:

bzr get SUBVERSION_URL PROJECT

it's also possible with tailor. Both claim to be able to continue to make commits on the subversion backend.

These commands have been tested with a HTTPS WEBDAV svn repository:

# Get a copy of the svn repository, like svn co
bzr get svn+https://svn_url PROJECT

# See what changes the svn repository has and what the local bzr repository has
bzr missing

# Push the commited changes from bzr to svn.
bzr push svn+https://svn_url PROJECT

# Pulls the latest changes from svn down into bzr
bzr merge

bzrtools

i make regular use of the shelf feature from bzrtools installed:

bzr shelve
bzr unshelve
bzr shelf ls
bzr shelf show
bzr shelf del

it allows you to set aside parts of revisions, even within individual files, to make it easier to commit only related changes.

additional and related topics

http://doc.bazaar-vcs.org/latest/en/mini-tutorial/index.html