Recently Pi Hole issued an update to there web front end, unfortunately every time I ran the command pihole -up I was getting an error message:

Unable to find remote helper for 'https'

I was struggling to find any help on the web about this error but stumbled on an old article regarding git cloning failing in a similar way, knowing that Pi Hole uses git I ran the following commands:

sudo apt-get remove git

and this command to re-install git and any missing components:

sudo apt-get install git-all

After this I re-issued the command pihole -up and was successfully able to update it to the latest.

pi@pihole:~ $ pihole -up
[i] Checking for updates...
[i] Pi-hole Core: up to date
[i] Web Interface: update available
[i] FTL: up to date

Hey Presto!