Format a file so that no line can exceed 72 characters (for git commit messages)

git commit formatter

# Outputs to shell. Could be updated to change file in place. Explanation here:
# https://stackoverflow.com/questions/26991777/regex-sed-how-to-match-the-last-space-character-in-a-line-before-a-72-charac?answertab=active#tab-top

sed 'y/ /³/
 s/.*/\
&³/
:space
 s/\(.*\n\)\([^³]\{0,72\}\)³/\1\2 /
 t space
 s/\(.*\) \([^³]*³\)/\1\
\2/
 t space
 s/.\(.*\)./\1/
 ' file.md