[openwrt/openwrt] build: improve message for incompatible image on "legacy" devices

[LEDE Commits]

adrian pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/fbd4214bb0727268aa535af5b600d38939ec8dbc

commit fbd4214bb0727268aa535af5b600d38939ec8dbc
Author: Adrian Schmutzler <freifunk at adrianschmutzler.de>
AuthorDate: Thu Aug 6 15:14:49 2020 +0200

    build: improve message for incompatible image on "legacy" devices
    
    It has been reported that the current message displayed during
    upgrade with compat_version change is misleading for "legacy"
    devices, i.e. those without the "new" fwtool. This is partially
    caused by the fact that we need to exploit the supported_devices
    string to get some message text displayed for these devices.
    
    This patch modifies the message to make it more helpful and
    include additional information, e.g.
    
      Device linksys,wrt3200acm not supported by this image
      Supported devices: linksys,wrt3200acm linksys-whateverelse - Image
      version mismatch: image 1.1, device 1.0. Please wipe config during
      upgrade (force required) or reinstall. Reason: Config cannot be
      migrated from swconfig to DSA
    
    Note that the line breaks (except the one before Supported devices)
    are added manually here, I hesitate to hack \n into the
    supported_devices as well. The "Reason:" will only be displayed if
    DEVICE_COMPAT_MESSAGE is set for the device, otherwise
    "Please check documentation ..." will be shown instead.
    
    While at it, also rearrange the code in image-commands.mk to
    make lines shorter and remove the double filter-out command.
    
    Signed-off-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
---
 include/image-commands.mk | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/image-commands.mk b/include/image-commands.mk
index 8ed705a7f4..9516801c8d 100644
--- a/include/image-commands.mk
+++ b/include/image-commands.mk
@@ -382,15 +382,20 @@ endef
 compat_version=$(if $(DEVICE_COMPAT_VERSION),$(DEVICE_COMPAT_VERSION),1.0)
 json_quote=$(subst ','\'',$(subst ",\",$(1)))
 #")')
+
+legacy_supported_message=$(SUPPORTED_DEVICES) - Image version mismatch: image $(compat_version), \
+	device 1.0. Please wipe config during upgrade (force required) or reinstall. \
+	$(if $(DEVICE_COMPAT_MESSAGE),Reason: $(DEVICE_COMPAT_MESSAGE),Please check documentation ...)
+
 metadata_devices=$(if $(1),$(subst "$(space)","$(comma)",$(strip $(foreach v,$(1),"$(call json_quote,$(v))"))))
 metadata_json = \
 	'{ $(if $(IMAGE_METADATA),$(IMAGE_METADATA)$(comma)) \
 		"metadata_version": "1.1", \
 		"compat_version": "$(call json_quote,$(compat_version))", \
 		$(if $(DEVICE_COMPAT_MESSAGE),"compat_message": "$(call json_quote,$(DEVICE_COMPAT_MESSAGE))"$(comma)) \
-		$(if $(filter-out 1.0,$(compat_version)),"new_supported_devices":[$(call metadata_devices,$(SUPPORTED_DEVICES))]$(comma)) \
-		$(if $(filter-out 1.0,$(compat_version)),"supported_devices": \
-			["$(call json_quote,Image version $(compat_version) incompatible to device: $(if $(DEVICE_COMPAT_MESSAGE),$(DEVICE_COMPAT_MESSAGE),Please check documentation ...))"]$(comma)) \
+		$(if $(filter-out 1.0,$(compat_version)),"new_supported_devices": \
+			[$(call metadata_devices,$(SUPPORTED_DEVICES))]$(comma) \
+			"supported_devices": ["$(call json_quote,$(legacy_supported_message))"]$(comma)) \
 		$(if $(filter 1.0,$(compat_version)),"supported_devices":[$(call metadata_devices,$(SUPPORTED_DEVICES))]$(comma)) \
 		"version": { \
 			"dist": "$(call json_quote,$(VERSION_DIST))", \