The binary is called gr.

Install 

  brew install d0ugal/tap/graith

Add the signing key and repository once, then install with apt-get:

  # add the signing key
curl -fsSL https://d0ugal.github.io/graith-repo/gpg/graith.gpg \
  | sudo tee /usr/share/keyrings/graith.gpg > /dev/null

# add the repo (signed-by pins it to our key only)
echo "deb [signed-by=/usr/share/keyrings/graith.gpg] \
https://d0ugal.github.io/graith-repo/deb stable main" \
  | sudo tee /etc/apt/sources.list.d/graith.list

sudo apt-get update
sudo apt-get install graith

apt-get upgrade then picks up new releases automatically.

  sudo tee /etc/yum.repos.d/graith.repo <<'EOF'
[graith]
name=graith
baseurl=https://d0ugal.github.io/graith-repo/rpm
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://d0ugal.github.io/graith-repo/gpg/graith.asc
EOF

sudo dnf install graith

dnf upgrade picks up new releases.

Download a binary for your platform from the releases page, extract it, and place gr on your $PATH.

On Debian/Ubuntu, Fedora/RHEL and Alpine you can instead grab a prebuilt .deb, .rpm or .apk package (linux amd64 and arm64; package name graith, binary gr, with shell completions), also from the releases page, and install it manually:

  # Debian / Ubuntu
sudo dpkg -i graith_*_linux_amd64.deb

# Fedora / RHEL
sudo rpm -i graith_*_linux_amd64.rpm

# Alpine
sudo apk add --allow-untrusted graith_*_linux_amd64.apk
  
  go install github.com/d0ugal/graith/cmd/graith@latest

go install names the binary after the package directory (graith). Rename or symlink it to gr:

  mv "$(go env GOPATH)/bin/graith" "$(go env GOPATH)/bin/gr"
  
  git clone https://github.com/d0ugal/graith
cd graith
make build    # produces ./gr

Shell completion

Generate completion scripts for your shell:

  # bash
source <(gr completion bash)

# zsh
gr completion zsh > "${fpath[1]}/_gr"

# fish
gr completion fish | source

# powershell
gr completion powershell | Out-String | Invoke-Expression

Verify 

  gr version
gr doctor      # health checks, verifies dependencies