You must distinguish between the svn ci -m message that you specify as a command line argument and the svn ci -F or svn ci --file version, which allows you to specify a commit message in the file.
The command line option is limited to the shell used; my script test stopped with a comment of just over 131,000 characters. With the version of the file name -F, I could commit tens of megabytes.
initall
source share