add installation guide for gogs on rpi

gogs/INSTALL.md

@@ -0,0 +1,40 @@
+Install Gogs On Raspberry Pi
+============================
+
+1. Install `git`.
+2. Download the latest binary from [here][1].
+3. Create a new user called `git`.
+4. Extract `raspi2.zip` to `/home/git`.
+5. Change the owner of `/home/git/gogs` to `git`.
+6. Create systemd unit file `gogs.service`.
+7. Start and enable `gogs.service`.
+8. Create a ssh port forwarding to `3000/tcp`.
+9. Open <http://localhost:3000> in web browser.
+
+## Install
+
+```bash
+sudo su
+apt install -y git
+cd /tmp
+wget https://github.com/gogits/gogs/releases/download/v0.9.13/raspi2.zip
+mkdir -p /home/git
+useradd -m -d /home/git -s /bin/bash git
+unzip raspi2.zip -d /home/git/
+chown -R git:git /home/git
+cp /home/git/gogs/scripts/systemd/gogs.service /etc/systemd/system/
+systemctl daemon-reload && systemctl start gogs && systemctl enable gogs
+rm raspi2.zip
+```
+
+## Setup
+
+In current SSH session, create a port forwarding to setup gogs.
+
+- Press: <kbd>~C</kbd>
+- Type: `-L 3000:localhost:3000`
+- Open: <http://localhost:3000/install>
+- Press: <kbd>~C</kbd>
+- Type: `-KL3000`
+
+[1]: https://github.com/gogits/gogs/releases