Change SVN commit message retroactively?
Solution 1:
Yes, commit messages can be changed. They are implemented as properties on revisions, similar to the regular file-properties.
In the TortoiseSVN Log window you can right click on a commit and select "Edit log message".
Solution 2:
You can certainly change log messages retroactively, it's covered in the FAQ. I'm not sure how the command line interface for VisualSVN works, but for vanilla svn the command would be
svn propset -r N --revprop svn:log "new log message" URL
If you want to do this for all revisions without dumping the repository and re-loading, you could script this command to work on a list of all revisions. It would take some time to do this way, depending on the size of your repository, but in principle there's no reason you can't do it, and it does not involve a dump and reload.
Also, vanilla SVN has a command svnlook
which is sort of an administrative tool that works directly with the repository files. That tool doesn't understand URLs (you must have filesystem-level access to the repository), but is much faster. The syntax is a little different, but you can modify properties in the same way using that tool.
Solution 3:
Yes, you can, but you need to enable it on the repository first.
In the repository, in the hooks directory, is a file called pre-revprop-change.tmpl. It's got a couple of pages of comments on what it does, and comes set up to only allow changes to the log properties. To enable it, rename the file to pre-revprop-change and make it executable (I'm assuming a POSIX-hosted subversion, if you're using Windows to host, you might find this message useful).
Once the repository allows it, you can use Tortoise to change the log message for a commit from the right-click menu on a commit, or you can use the command line.