Is it safe to do everything from the main project? Can the main project use svnant to update itself, or if svn needs to update the build.xml file currently used by ant, will there be problems?
If you really have to update the build.xml reliably and execute the build in one go, you can consider including the post-svnant part of the build in the antcall task. When Ant runs the target of antcall, It re-reads build.xml, so any changes to the file after calling Ant will be taken into account. Antcall is processed from the beginning, so if you have (possibly expensive) initialization, you will need to run it again.
I am maintaining a build system that uses svnant from one directory to update a large number of items in another directory. Then it moves to one of those items that have been updated, And do the actual build.
Is it safe to do everything from the main project? Can the main project use svnant to update itself, or if svn needs to update the build.xml file currently used by ant, will there be problems?
For the self-updating main project build.xml-you may encounter problems running subversion updates and a build. The nature of the problem depends on the build. What changes have been made to the xml. Simply re-running the build may fix it, because the build.xml Ant loaded at startup will be the latest.
If you really have to update the build reliably .xml and execute the build one time, you can consider including the post-svnant part of the build in the antcall task. When Ant runs the target of antcall, it will re-read the build.xml, so when calling Any changes to this file after Ant will be taken into account. Antcall is processed from the beginning, so if you have a (possibly expensive) initialization, you will need to run it again.