Start tracking svnmerge info when we create a branch

I thought it was tracked by default

archrelease

@@ -9,6 +9,11 @@ if [ ! -d ../repos/$1 ]; then
     pushd ..
     svn copy -r HEAD trunk repos/$1
     svn commit -m "archrelease: new repo $1"
+    pushd repos/$1
+    svnmerge init
+    svn commit -F svnmerge-commit-message.txt
+    rm svnmerge-commit-message.txt
+    popd
     popd
 else
     svnmerge merge ../repos/$1