templates: boot_stack, but dd

To go alongside recovery_install_dd, for the few unfortunate devices
out there that don't have a fastboot at all.

Change-Id: Ibfee4559c4c732b0e59ea0c052583dd8394e7df6

_includes/templates/device_specific/before_recovery_install_boot_stack_dd.md

@@ -0,0 +1,33 @@
+## Flashing additional partitions
+
+{% include alerts/warning.html content="This platform requires additional partitions to be flashed for recovery to work properly, the process to do so is described below." %}
+
+1. Download the following files from [here](https://download.lineageos.org/devices/{{ device.codename }}).
+{%- for partition in device.before_recovery_install.partitions %}
+  * {{ partition }}.img
+{%- endfor %}
+2. Place the files on the root of `/sdcard`:
+   * Using adb:
+      ```
+{%- for partition in device.before_recovery_install.partitions %}
+      adb -d push {{ partition }}.img /sdcard/{{ partition }}.img
+{%- endfor %}
+      ```
+   * You can use any method you are comfortable with. `adb` is universal across all devices, and works both in Android and recovery mode, providing USB debugging is enabled.
+3. Now, open an `adb -d shell` from a command prompt (on Windows) or terminal (on Linux or macOS) window. In that shell, type the following commands:
+{%- if device.is_ab_device %}
+```
+su
+{%- for partition in device.before_recovery_install.partitions %}
+dd if=/sdcard/{{ partition }}.img of={{ partition }}_a
+dd if=/sdcard/{{ partition }}.img of={{ partition }}_b
+{%- endfor %}
+```
+{%- else %}
+```
+su
+{%- for partition in device.before_recovery_install.partitions %}
+dd if=/sdcard/{{ partition }}.img of={{ partition }}
+{%- endfor %}
+```
+{%- endif %}