Transcript Document

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Subversion
Kate Hedstrom
April 2007
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Version Control Software
• System for managing source files
– For groups of people working on the same
code
– When you need to get back last week’s
version
• In the old days, there was SCCS and RCS for
file-wise management
• Then came CVS
– Works with whole directory trees
– Has a network option for remote access
• Newest is SVN, which attempts to fix the
shortcomings in CVS
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Getting Started With SVN
• Tell it where the archive is with a
URL:
file:///local/path
or
http://host/path
• Mine is in nanook’s /archive, visible
to Sun and iceflyer
• For a new archive:
% svnadmin create /local/path
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Main svn commands
• import - bring sources into the repository
• checkout - get sources out of the
repository
• commit - check in changes
• update - get changes from repository
• status - find out which files would change
on commit
• diff - find out what changed
• help
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Example
• The svn people advise setting up
a directory tree with
subdirectories
– trunk
– tags
– branches
• Your actual code goes in trunk
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% ls /tmp/cpp
branches
tags
trunk
# import whole directory
% svn import /tmp/cpp \
file:///local/path -m “initial import”
% rm -rf /tmp/cpp
# want to be working in checked-out copy
% svn checkout \
file:///local/path/cpp/trunk cpp
% cd cpp
[make some changes]
% svn commit
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Coordination
# on iceflyer
% svn checkout <URL> roms
% cd roms
[make some changes]
% svn commit
#
%
%
%
%
on cygnus
svn checkout …
cd roms
svn update
make
• Coordinate code on multiple systems
• Coordinate between multiple
programmers
• Can be common version or different
branches
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Updates
• An update when two people have
changed things can involve:
– No conflict because changes are in
different places
– Conflict because two different changes to
the same region in the code
• If there is a conflict this must be
resolved by human intervention
• One option is to revert (undo)
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Other svn commands
• add - add a new file or directory to svn
control
• delete - no longer need a file
• move - rename a file or move to new
location
• merge - merge changes from another
branch
• info - find URL used
• copy - make branches and tags
• switch - switch working directory to a
different branch
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Revision Numbers
• svn uses a database to store the files
• The whole project as one revision
number across the whole project to
describe that snapshot
• Can see the numbers with “svn log”
• This is different from CVS, which
keeps a different number for each file
(uses filewise RCS for repository)
• Every commit creates a new revision
number
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Branches
• Branch can be just for one or a few files
or the whole ROMS tree
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Tags
• Tags are handled like branches
• Create a working version that goes
together and make a branch in the
tags directory with the name of the
tag (release_1.0, say)
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ROMS Example
• ROMS comes from a read-only
repository:
svn checkout <URL> hernan_roms
• Make own repository where that
version is the trunk
– Copy it to another location without the .svn
files
– Import it into your repository
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• Now make a branch for your version:
svn copy <URL1> <URL2>
• These have to be in the same
repository
• It is currently a copy of the main ROMS
code - edit it with your changes and
check it back in
svn checkout <URL2>
Edit…
svn commit
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• So, Hernan has made some changes,
what now?
• Go to your copy of his code from his
repository:
svn update
• Make note of files that were added and
deleted
• Copy to the trunk part of your
repository:
tar cvf - --exclude .svn | (cd
../roms_trunk; tar xvf -)
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• In your trunk directory, add and
delete the files you noted before:
svn add new files…
svn delete old files…
• Check status, then check in:
svn status
svn commit
• Make note of the version number
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• Doing the actual merge - in the
directory for your branch (URL2):
svn merge -r 41:45 <URL1>
• Resolve conflicts, if any
• Check in the update, making note of
the revision numbers and <URL1>
svn ci -m “merge from -r 41:45
<URL1>”
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ROMS Summary
• Each directory has .svn files
pointing to its URL
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Conflicts
• If there is a conflict, svn will
provide you with four files:
– The original file (filename.mine)
– The older file from the trunk (filename.r41)
– The newer file from the trunk (filename.r45)
– A merge attempt (filename)
• The merge failures will look
something like:
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Clean code before
<<<<<<< .mine
My code
=======
New code
>>>>>>> .r45
Clean code after
• Once you’ve cleaned up the mess, tell svn
you’re ready:
svn resolved filename
• This will cause svn to delete the extra files
and allow a commit to take place
• You can instead toss your changes with:
svn revert filename
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Learn more
• Version Control with Subversion, by
Collins-Sussman et al., 2004, O’Reilly
• Online at http:svnbook.red-bean.com/
• svn help