If you need to make changes to a large source tree with an .externals defining the source tree, (like sakai) it can be a pain, so its better to do it with a script perhapse.

for i in `find . -name m2-target` ; do pushd `dirname $i`; echo m2-target > svnsettarget; svn propget svn:ignore grep -v m2-target » svnsettarget; cat svnsettarget; svn propset svn:ignore -F svnsettarget . ; rm svnsettarget; popd; done

followed by

for i in `ls -l | grep “^d” | cut -c45-`; do pushd $i; svn commit -m ‘Adding ignore for m2-target’; popd; done

Will add to and commit changes to svn:ignore.