Comment # 29 on bug 1165780 from Karl Mistelberger

When duping to 20200417 I tested the following minimal units:

# /etc/systemd/system/btrfsmaintenance-refresh.path
[Unit]
Description=Watch /etc/sysconfig/btrfsmaintenance

[Path]
PathChanged=/etc/sysconfig/btrfsmaintenance

[Install]
WantedBy=multi-user.target

# /etc/systemd/system/btrfsmaintenance-refresh.service
[Unit]
Description=Update cron periods from /etc/sysconfig/btrfsmaintenance

[Service]
ExecStart=/usr/share/btrfsmaintenance/btrfsmaintenance-refresh-cron.sh
systemd-timer
Type=oneshot

UNIT FILE                        STATE   VENDOR PRESET
btrfsmaintenance-refresh.path    enabled disabled     
btrfsmaintenance-refresh.service static  enabled      

Apr 21 10:16:25 systemd[1]: Started Watch /etc/sysconfig/btrfsmaintenance.
Apr 21 10:16:40 systemd[1]: Started Balance block groups on a btrfs filesystem.
Apr 21 10:16:40 systemd[1]: Started Defragment file data and/or directory
metadata.
Apr 21 10:16:40 systemd[1]: Started Scrub btrfs filesystem, verify block
checksums.

Seems to work as intended.