SVN Page

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Catherine suggested that we put all the bits and pieces we learn about SVN in one place. A jolly good idea as I do tend to forget about things!

As a CVS user, migrating to SVN was not without it's hiccoughs. I found the biggest one to be that SVN commands like svn diff, svn status (and maybe a few more) work against the pristine revision located in the .svn subdirectory in your working directory and not the latest revision in the SVN repository. In contrast, CVS commands always work against the latest revision in the CVS repository.

In the discussion that follows, call the pristine revision in the working directory BASE and the latest revision in the SVN repository HEAD.

Another hiccough is the use of revision numbers. This topic has been dealt with very well in the Subversion book [1]. See the section on SVN DIFF for a discussion of some of the issues related to version numbers that might make a CVS user weep.

--alston 18:10, 28 November 2006 (GMT)

SVN Links

Setting up your SVN details

(1) If you've got an account on the SVN server at WWMM, you should have a certificate file need by SVN to authenticate a session. Let's call this file svn_cert.p12. Place it in a convenient place, say, $HOME/certificates/

(2) Now edit the file $HOME/.subversion/servers It should contain the lines: 

[groups]
wwmm = wwmm.ch.cam.ac.uk
                                                                                
[wwmm]
ssl-client-cert-file = $HOME/certificates/svn_cert.p12
ssl-client-cert-password = <the password Catherine gave you>

I'm not sure if you have to put your password there, but if you do, SVN won't prompt you for a password each time you try to use it.

(3) I found it convenient to define an environment variable pointing to my SVN directory on the WWMM server: 

SVN=https://wwmm.ch.cam.ac.uk/svn/users/am592
export SVN

You could just add those lines to your .bashrc file.

Now you are set.

--alston 14:22, 31 October 2006 (GMT)

Creating a Project

There seem to be a couple of ways of doing this. The method reccommended by the SVN book (Version Control with Subversion - O'Reilly) is to use svnadmin create. This won't work as none of us users have access to the svnadmin command. The following works quite well: 

$ svn mkdir $SVN/project1

This will create directory project1 in the repository. The svn mkdir command can also be used to make a directory in your working copy, but more on this later.

Now your project has its own directory on the SVN server. Let's get the files into it. 

$ ls my_code
a.f90  b.f90
$ svn import my_code $SVN/project1
Adding     my_code/a.f90
Adding     my_code/b.f90
Committed revision 1.

That's done. Notice that the project is called my_code in my directory but project1 on the server. The names could be the same. --alston 14:22, 31 October 2006 (GMT)

Checking out a project

To check out a project from the repository: 

$ svn checkout $SVN/project1 [PATH]

where $SVN/project1 is the URL for the project in the repository. If PATH is not given, subversion will create the same directory structure for you (if PATH is given, it will create any directories which don't exist).

svn co is shorthand for the svn checkout.

--james 13:50, 31 October 2006 (GMT)

Committing changes

To commit your local changes to the repository: 

svn commit
svn update

svn commit will take you into your default editor (vi, hopefully) for you to enter your (suitably verbose) log message and show which paths have been changed. svn update brings your working (BASE) copy up-to-date with the HEAD version.

If the log message is short, you can specify it on the command line: 

svn ci -m 'log message'

ci is short for commit.

If you wish to only commit some of the changed files, then specify them: 

svn ci [PATH]

By default, all local changes are committed to the repository. --james 13:51, 5 December 2006 (GMT)

Help

svn help <command> is very useful, as is the O'Reilly book, which available free online (and for download) here: SVN book.

--james 12:34, 31 October 2006 (GMT)

Differences

It's exceptionally useful to check the difference between a local file and the repository version. svn does provide svn diff, but this uses the standard diff engine, which is somewhat unhelpful. You (apparently) can change your diff engine (e.g. to xxdiff) in your ~/.subversion/config file, but I have never got this to work. Instead, I wrote a function using svn cat in my ~/.bashrc which does the job: 

svndiff () {
    if [ "$#" -eq 0 -o "$1" == "-help" -o "$1" == "--help" ];    then
        echo "Usage: svndiff <file> [-r revision_number]"
        echo "Compare local copy to specified revision in the subversion"
        echo "repository (default: last commit) using xxdiff."
    else
        svn cat $@ | xxdiff $1 - --title2 "Repository copy $1"
    fi
}

xxdiff is now installed on the workstations and servers (or, e.g., vimdiff can be used).

--james 11:30, 5 December 2006 (GMT)

I just found this version of svndiff ( http://svn.sunbase.org/repos/svnutils/trunk/src/svndiff) that is a bit more powerful than the above one (sorry James, but this one can use a choice of diff programs and allows you to use -r N:M). I'm placing a slightly modified copy here. --alston 14:15, 5 December 2006 (GMT)

CVS users use cvs diff in just two ways. The default behaviour of cvs diff is to difference a file against the latest version in the CVS repository. If a difference against a particular revision of a file was needed, a CVS user might use cvs diff -r N file.name. Things are different with SVN. First of all, the default behaviour of svn diff is to show only local differences; that is, differences against the pristine copy in the working copy (the BASE). Second, while you could use the command svn diff -r N file.name, since SVN maintains global revision numbers, version N of your file is quite likely the same as your current version. SVN provides a different set of commands to take care of these issues.

There are three kinds of differences you'd probably like to make:

(1) A difference against the latest version in the repository: 

svn diff -r HEAD <file.name>
or, if you've defined James' command (above),
svndiff <file.name> -r HEAD

As described in the preamble, HEAD refers to the latest version in the SVN repository.

(2) A difference against the pristine version of the file in the working copy: 

svn diff <file.name>
or
svn diff -r BASE <file.name>
or
svndiff <file.name>
or
svndiff <file.name> -r BASE

So this is the default behaviour of svn diff. The BASE is optional.

(3) The latest revision in the repository could be the same as the BASE version, so SVN provides a way of differencing against the last revision at which the item changed before the BASE: 

svn diff -r COMMITTED <file.name>
or
svndiff <file.name> -r COMMITTED

SVN also proivides a way of accessing the revision just before the last revision at which the item changed: 

svn diff -r PREV <file.name>
or
svndiff <file.name> -r PREV

Though I still haven't found a situation in which I would want to use this.--alston 11:18, 30 November 2006 (GMT)

If you'd like differences against a revision of a file/directory earlier than possible using the above tags, first use svn log <file.name> to figure out the revision numbers needed. svn log will print logs for only those revisions in which your file/directory changed. Then use svndiff <file.name> -r N where N is the revision number.

PREV could be useful if you committed code without testing it and then realised it was wrong. Of course, we'd never be so incompetent... --james 11:45, 15 January 2007 (GMT)

Logs

Logs can quickly become very length, so I find piping svn log through less is a good option (particularly as I tend to be more interested in recent changes). Note that unless you specify a revision number, you will only see the logs of commits from before your last update (so if you commit code, you won't see your own log message until you update your local version).

The verbose flag prints out the changed paths as well (very handy!): 

svn log -v | less

--james 13:41, 5 December 2006 (GMT)

I got this from the SVN FAQ (online): 

How can I make svn diff show me just the names of the changed files, not their contents?

svn diff doesn't have an option to do this, but

    * If you only are interested in the diffs between, say, revision 10 and the revision just before it,

      svn log -vq -r10

      does exactly what you want;
    * otherwise, if you're using Unix, this works for any range of revisions:

          svn log -vq -r123:456 | egrep '^ {3}[ADMR] ' | cut -c6- | sort | uniq

It's rather useful. --alston 14:02, 5 December 2006 (GMT)

Like most SVN commands, the default behaviour of svn log file.name is to give you the log messages of file.name as it is in your working copy, i.e., BASE. You may want the logs of the file as it is in the repository, i.e., the HEAD. To do this use: 

svn log -r HEAD file.name

If you want the log messages of the file since your copy was checked out, use 

svn log -r BASE:COMMITTED file.name
or
svn log -r BASE:HEAD file.name

I have yet to test to see which one works best. --james 18:25, 17 January 2007 (GMT)

Status

svn status returns the status of all the files in the current directory (or the path specified). This is a pain if you have lots of files produced by compiling your code/tex files, Makefiles and the ilk, which are not (and should not be) under source code management. svn status returns these marked by ?, which is not good if you have a few hundred such files. Fortunately, there is a way to change this! Open up ~/.subversion/config in your favourite text editor (which ought to be vi). Lines starting with # are comment lines. Uncomment [miscellany] and global-ignores. In the global ignores line, add any filenames and extensions you wish to ignore (e.g. *.o).

svn info gives you some useful information on a file/path (or current directory if no path is specified).

--james 12:44, 31 October 2006 (GMT)

svn status will return the status of your working copy with respect to your pristine copy located in the .svn sub-directory (the BASE).

If you wish to find out the status of your working copy with respect to the SVN repository (the HEAD), use 

svn status --show-updates
or
svn status -u

This is non-intitutive for CVS users as cvs status always returns the status of the working copy w.r.t. the CVS repository.

--alston 16:57, 28 November 2006 (GMT)

Reverting

So, you have made some changes to your code and committed them, and now realise that your changes break everything. One of the strengths of using subversion (and other source code management systems) is to allow you to rollback code, however this is not intuitive in subversion.

svn revert <filename> reverts your *local* version back to the repository version. It doesn't accept a -r flag, so you can't use it to go back to older versions in the repository. It is useful if you've made some temporary changes for testing purposes, as you can revert to your clean code with one command).

(As an aside svn revert -R . will revert all files in the current and lower directories.)

To rollback to a previous version, first you need to find out which revision number you want to revert to. Then use svn update in a cunning way: 

svn update -r <revision number>

--james 13:45, 31 October 2006 (GMT)

Errors

  • Seg fault in VIM when attempting to type in LOG message:
$ svn commit
(VIM is opened and you enter edit mode; press a key; and...)
svn: Commit failed (details follow):
--This line, and those below, will bsvn: system('vim -c 'set tw=72 et'
svn-commit.tmp') returned 11
M    BIBLIOGRAPHY.bi[am592@radiant Induction]$ bash: 1: command not found
M    tables/E3int.tex

The formatting in your terminal is destroyed and you need to type: 

$ reset

Of course you could use svn commit -m "your message goes here", but this doesn't allow multiline log messages.

I found the following workaround. In your .bashrc file include the statement: 

alias svncommit='svn commit --editor-cmd vim'

Now use the command svncommit instead of svn commit. This seems to work - at least I haven't seen the SEG fault since doing this. --alston 13:03, 13 December 2006 (GMT)

This is very odd: do you see this error every time, or only occasionally? I've never had such a problem. It could be a bizarre local configuration problem?

You could also try uncommenting the [helpers] and editor-cmd in your ~/.subversion/config file; I'd be interested to see if that also worked.

--james 13:47, 13 December 2006 (GMT)

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