After 7c4024da667a889c7b4e2146040324f763c33c86, I can no longer install a local plugin that has a capital letter in the path, as test -e $plugin will always fail and attempt to download the plugin from GitHub.
$ fisher install $HOME/Dev/github/env/fish
fisher install version 4.4.2
Fetching https://api.github.com/repos//home/nathan/dev/github/env/fish/tarball/HEAD
fisher: Invalid plugin name or host unavailable: "/home/nathan/dev/github/env/fish"
After 7c4024da667a889c7b4e2146040324f763c33c86, I can no longer install a local plugin that has a capital letter in the path, as
test -e $plugin
will always fail and attempt to download the plugin from GitHub.