The Perl program md2tweets.pl is a companion to tumblelog; it reads the input file of tumbelog and outputs tweets separated by '%', a format used by tweetfile.
For example:
md2tweets --template-filename tweet.txt --blog-url https://plurrrr.com/ \
plurrrr.md > tweets.txt
Docker example:
docker run --rm --volume "`pwd`:/data:ro" --user `id -u`:`id -g` \
md2tweets --template-filename tweet.txt --blog-url https://plurrrr.com/ \
plurrrr.md > tweets.txt