Add initial version of lineageos unbricking

This should be a series, or a heavily updated post ... not sure if I'd have
enough time and energy would.

source/blog/upgrade-lineageos.rst

@@ -0,0 +1,70 @@
+.. post:: 2021.04.26
+   :tags: howto,lineageos,upgrade
+   :category: android
+   :author: vladan
+   :location: Ohrid
+
+====================================
+Upgrading LineageOS on OnePlus 7 Pro
+====================================
+
+.. warning::
+   Always backup everything!!!
+
+FIRST (update recovery img)
+===========================
+
+Update the recovery img with::
+
+    fastboot flash boot_a ~vladan/Downloads/twrp-3.5.2_9-0-guacamole.img
+
+The ``a`` in ``boot_a`` is the output of ``fastboot getvar current-slot`` because
+the installation didn't have a recovery partition. The boot partition is used
+for recovery, hence the command above. More info `here
+<https://forum.xda-developers.com/t/no-such-partition.3733811/#post-75165281>`_.
+
+
+.. warning::
+
+    If this is not done in the first place, then `download twrp
+    <https://eu.dl.twrp.me/guacamole/>`_ and boot it. I ran into a boot loop
+    because I didn't do this in the first place and had to resort to TWRP.
+
+To work around this issue, run::
+
+    fastboot boot /home/vladan/Downloads/twrp-installer-3.5.2_9-0-guacamole.zip
+
+
+Manually flash all partitions
+=============================
+
+.. code:: bash
+
+    git clone https://github.com/vladan/payload_dumper.git
+
+    python payload_dumper.py --diff payload.bin
+
+    cd output
+
+    fastboot -w
+    fastboot flash aop aop.img
+    fastboot flash bluetooth bluetooth.img
+    fastboot flash boot boot.img
+    fastboot flash dsp dsp.img
+    fastboot flash dtbo dtbo.img
+    fastboot flash LOGO LOGO.img
+    fastboot flash modem modem.img
+    fastboot flash oem_stanvbk oem_stanvbk.img
+    fastboot flash qupfw qupfw.img
+    fastboot flash storsec storsec.img
+    fastboot flash multiimgoem multiimgoem.img
+    fastboot flash uefisecapp uefisecapp.img
+    fastboot flash recovery recovery.img
+    fastboot --disable-verity flash vbmeta vbmeta.img
+    fastboot --disable-verity flash vbmeta_system vbmeta_system.img
+    fastboot flash opproduct opproduct.img
+    fastboot reboot bootloader
+    fastboot flash system system.img
+    fastboot flash vendor vendor.img
+    fastboot flash product product.img
+    fastboot reboot