xdg-email fails to attach filesnames with a comma "," to thunderbird

When attaching a file to Thunderbird using xdg-email, it passes the full path to Thunderbird, as possible with TB3+. However, the syntax of TB uses the comma "," as filename separator. If a filename already contains a comma, Thunderbird will not find it and fails to attach it.

This could probably be fixed in Thunderbird, but would require them to change their command line syntax which is a big change. A different solution is to change from the "full path" syntax to "file://<path>" using a full URL-encodeing?

Example: the file is located at "/home/someuser/file, name.txt"

Calling xdg-email with "xdg-email --attach '/home/someuser/file, name.txt'" will produce (XDG_UTILS_DEBUG_LEVEL=1)

/usr/lib/thunderbird/thunderbird.sh -compose "attachment='/home/someuser/file, name.txt'"

And Thunderbird expects two files now, one "/home/someuser/file" and the other "name.txt". Instead

/usr/lib/thunderbird/thunderbird.sh -compose "attachment='file///home/someuser/file%2C%20name.txt'"

works.

As it turned out, not much needs to be changed. I created a crude patch to change from "file name scheme" to "uri scheme" against the version below with (for me) solves the issue. Note that I'm not a bash expert, so the solution might give room for improvement.

Some information:
>apt policy xdg-utils
xdg-utils:
  Installiert: 1.1.2-1ubuntu2.3
  Installationskandidat: 1.1.2-1ubuntu2.3

lsb_release will list Linux Mint Tess (19.1), upstream based on Ubuntu Bionic (hence the bug reported here)