Unset nerves_fw_active to avoid confusion

This completely removes the `nerves_fw_active` U-Boot environment
variable on upgrades so that stale versions don't exist. It also cleans
up `nerves_fw_validated` to only be the slot-specific versions.

This shouldn't change or break anything so long as relatively up to date
versions of `Nerves.Runtime` are being used.

Author: fhunleth

fwup.conf

@@ -72,7 +72,6 @@ task complete {
 
         include("${NERVES_PROVISIONING}")
 
-        uboot_setenv(uboot-env, "nerves_fw_active", "a") # mirrors autoboot.txt
         uboot_setenv(uboot-env, "nerves_fw_devpath", ${NERVES_FW_DEVPATH})
         uboot_setenv(uboot-env, "a.nerves_fw_validated", "1")
         uboot_setenv(uboot-env, "a.nerves_fw_application_part0_devpath", ${NERVES_FW_APPLICATION_PART0_DEVPATH})
@@ -218,10 +217,12 @@ task upgrade.old-a {
         uboot_setenv(uboot-env, "a.nerves_fw_vcs_identifier", ${NERVES_FW_VCS_IDENTIFIER})
         uboot_setenv(uboot-env, "a.nerves_fw_misc", ${NERVES_FW_MISC})
         uboot_setenv(uboot-env, "a.nerves_fw_uuid", "\${FWUP_META_UUID}")
+        uboot_unsetenv(uboot-env, "nerves_fw_active") # No longer used
+        uboot_unsetenv(uboot-env, "nerves_fw_validated") # No longer used
 
-	# Switch over to boot the new firmware but validate since can't go back
-        uboot_setenv(uboot-env, "nerves_fw_active", "a") # mirrors autoboot.txt
+        # Validate since can't go back
         uboot_setenv(uboot-env, "a.nerves_fw_validated", "1")
+        uboot_setenv(uboot-env, "b.nerves_fw_validated", "0")
         mbr_write(mbr)
     }
 }
@@ -304,10 +305,12 @@ task upgrade.old-b {
         uboot_setenv(uboot-env, "b.nerves_fw_vcs_identifier", ${NERVES_FW_VCS_IDENTIFIER})
         uboot_setenv(uboot-env, "b.nerves_fw_misc", ${NERVES_FW_MISC})
         uboot_setenv(uboot-env, "b.nerves_fw_uuid", "\${FWUP_META_UUID}")
+        uboot_unsetenv(uboot-env, "nerves_fw_active") # No longer used
+        uboot_unsetenv(uboot-env, "nerves_fw_validated") # No longer used
 
-	# Switch over to boot the new firmware but validate since can't go back
-        uboot_setenv(uboot-env, "nerves_fw_active", "b") # mirrors autoboot.txt
+        # Validate since can't go back
         uboot_setenv(uboot-env, "b.nerves_fw_validated", "1")
+        uboot_setenv(uboot-env, "a.nerves_fw_validated", "0")
         mbr_write(mbr)
     }
 }

fwup.conf.eex

@@ -77,7 +77,6 @@ task complete {
 
         include("${NERVES_PROVISIONING}")
 
-        uboot_setenv(uboot-env, "nerves_fw_active", "a") # mirrors autoboot.txt
         uboot_setenv(uboot-env, "nerves_fw_devpath", ${NERVES_FW_DEVPATH})
         uboot_setenv(uboot-env, "a.nerves_fw_validated", "1")
         uboot_setenv(uboot-env, "a.nerves_fw_application_part0_devpath", ${NERVES_FW_APPLICATION_PART0_DEVPATH})
@@ -175,10 +174,12 @@ task upgrade.old-a {
         uboot_setenv(uboot-env, "a.nerves_fw_vcs_identifier", ${NERVES_FW_VCS_IDENTIFIER})
         uboot_setenv(uboot-env, "a.nerves_fw_misc", ${NERVES_FW_MISC})
         uboot_setenv(uboot-env, "a.nerves_fw_uuid", "\${FWUP_META_UUID}")
+        uboot_unsetenv(uboot-env, "nerves_fw_active") # No longer used
+        uboot_unsetenv(uboot-env, "nerves_fw_validated") # No longer used
 
-	# Switch over to boot the new firmware but validate since can't go back
-        uboot_setenv(uboot-env, "nerves_fw_active", "a") # mirrors autoboot.txt
+        # Validate since can't go back
         uboot_setenv(uboot-env, "a.nerves_fw_validated", "1")
+        uboot_setenv(uboot-env, "b.nerves_fw_validated", "0")
         mbr_write(mbr)
     }
 }
@@ -238,10 +239,12 @@ task upgrade.old-b {
         uboot_setenv(uboot-env, "b.nerves_fw_vcs_identifier", ${NERVES_FW_VCS_IDENTIFIER})
         uboot_setenv(uboot-env, "b.nerves_fw_misc", ${NERVES_FW_MISC})
         uboot_setenv(uboot-env, "b.nerves_fw_uuid", "\${FWUP_META_UUID}")
+        uboot_unsetenv(uboot-env, "nerves_fw_active") # No longer used
+        uboot_unsetenv(uboot-env, "nerves_fw_validated") # No longer used
 
-	# Switch over to boot the new firmware but validate since can't go back
-        uboot_setenv(uboot-env, "nerves_fw_active", "b") # mirrors autoboot.txt
+        # Validate since can't go back
         uboot_setenv(uboot-env, "b.nerves_fw_validated", "1")
+        uboot_setenv(uboot-env, "a.nerves_fw_validated", "0")
         mbr_write(mbr)
     }
 }