Simplify nerves-config and select required packages

A whole lot of this hasn't been used in a long time so I started
deleting parts. The automatic selection of required packages is pretty
convenient so I added a few more to simplify system configuration.

Author: fhunleth

package/nerves-config/Config.in

@@ -3,73 +3,17 @@ menuconfig BR2_PACKAGE_NERVES_CONFIG
 	select BR2_PACKAGE_ERLANG   # Erlang is required for all Nerves systems
 	select BR2_PACKAGE_ERLINIT  # Always use erlinit to boot
 	select BR2_PACKAGE_OPENSSL  # Used for Erlang crypto
+	select BR2_PACKAGE_FWUP     # Used for OTA firmware updates
+	select BR2_PACKAGE_NCURSES  # IEx shell is near impossible to use without
+	select BR2_PACKAGE_UBOOT_TOOLS  # Required for Nerves firmware metadata
+	select BR2_PACKAGE_BOARDID  # ID board for assigning unique names
 	select BR2_PACKAGE_HOST_FWUP # Used by Nerves packaging tools
 	select BR2_PACKAGE_HOST_ERLANG_RELX # Used to create test .fw file
+	select BR2_TARGET_ROOTFS_SQUASHFS # Nerves uses squashfs archives
 	help
-	  Nerves system configuration helper
+	  Nerves system configuration helper. This selects a set of packages
+	  used by all Nerves systems so that they're never accidentally omitted.
+	  This package used to do more, but has been trimmed down as functionality
+	  has moved into the Nerves tooling.
 
 	  https://github.com/nerves-project/nerves_system_br
-
-if BR2_PACKAGE_NERVES_CONFIG
-
-choice
-        prompt "erlinit.config"
-        default BR2_PACKAGE_NERVES_CONFIG_GENERATE_ERLINIT_CONF
-        help
-          Select source of erlinit.config
-
-config BR2_PACKAGE_NERVES_CONFIG_SPECIFY_ERLINIT_CONF
-        bool "Specify erlinit.config"
-        help
-          Specify a path to an erlinit.config.
-
-config BR2_PACKAGE_NERVES_CONFIG_NO_ERLINIT_CONF
-        bool "No erlinit.config"
-        help
-          Do not include an erlinit.config. The generated image won't boot unless
-          one is added using another mechanism.
-endchoice
-
-if BR2_PACKAGE_NERVES_CONFIG_SPECIFY_ERLINIT_CONF
-
-config BR2_PACKAGE_NERVES_CONFIG_ERLINIT_CONF_PATH
-	string "Path to erlinit.config"
-	default ""
-	help
-	  Specify a path to erlinit.config
-
-endif
-
-config BR2_PACKAGE_NERVES_CONFIG_APPS
-        string "Erlang apps to include"
-        help
-          Space-separated list of Erlang apps to include in the base
-          Nerves image. The apps must be already be built or relx will
-          fail.
-
-config BR2_PACKAGE_NERVES_CONFIG_DISTRIBUTION
-        bool "Enable Erlang distribution"
-        default y
-        help
-          Enable Erlang distribution. You will also need to bring up the
-          appropriate network interfaces at runtime for this to work.
-
-if BR2_PACKAGE_NERVES_CONFIG_DISTRIBUTION
-config BR2_PACKAGE_NERVES_CONFIG_SNAME
-	string "sname"
-	default "demo"
-	help
-	  Use the specified simple name for this node. This will be the
-	  sname for all nodes running the firmware release, so if you have
-	  multiple nodes running the same firmware, it is better to set the
-	  node name at runtime.
-
-config BR2_PACKAGE_NERVES_CONFIG_COOKIE
-	string "cookie"
-	default "democookie"
-	help
-	  The cookie to use for distributed Erlang
-endif
-
-endif
-

package/nerves-config/nerves-config.mk

@@ -7,39 +7,26 @@
 # Remember to bump the version when anything changes in this
 # directory.
 NERVES_CONFIG_SOURCE =
-NERVES_CONFIG_VERSION = 0.5
+NERVES_CONFIG_VERSION = 0.6
 
 NERVES_CONFIG_DEPENDENCIES = erlinit erlang host-erlang-relx host-fwup openssl
 
 NERVES_CONFIG_PACKAGE_DIR = $(BR2_EXTERNAL_NERVES_PATH)/package/nerves-config
 NERVES_CONFIG_ERLANG_RELEASE_DIR = $(TARGET_DIR)/srv/erlang
 
-NERVES_CONFIG_EXTRA_APPS += stdlib
-NERVES_CONFIG_ALL_APPS = $(subst $(space),$(comma),$(call qstrip,$(BR2_PACKAGE_NERVES_CONFIG_APPS) $(NERVES_CONFIG_EXTRA_APPS)))
-
 define NERVES_CONFIG_BUILD_CMDS
 	# Create the relx configuration file
-	m4 -DAPPS="$(NERVES_CONFIG_ALL_APPS)" \
-	    $(NERVES_CONFIG_PACKAGE_DIR)/relx.config.m4 > $(@D)/relx.config
+	m4 $(NERVES_CONFIG_PACKAGE_DIR)/relx.config.m4 > $(@D)/relx.config
 
 	# Create the vm.args file for starting the Erlang runtime
-	m4 -DDISTRIBUTION=$(BR2_PACKAGE_NERVES_CONFIG_DISTRIBUTION) \
-	    -DSNAME=$(BR2_PACKAGE_NERVES_CONFIG_SNAME) \
-	    -DCOOKIE=$(BR2_PACKAGE_NERVES_CONFIG_COOKIE) \
-	    $(NERVES_CONFIG_PACKAGE_DIR)/vm.args.m4 > $(@D)/vm.args
+	m4 $(NERVES_CONFIG_PACKAGE_DIR)/vm.args.m4 > $(@D)/vm.args
 
 	# Run relx to create a sample release. Real projects will have
 	# their own relx.config scripts and be in a separate repo, but
 	# this release is a good one for playing around with Nerves.
 	NERVES_SDK_SYSROOT=$(HOST_DIR) $(RELX) $(NERVES_CONFIG_RELX_LIBDIRS) --vm_args $(@D)/vm.args -c $(@D)/relx.config
 endef
 
-ifeq ($(BR2_PACKAGE_NERVES_CONFIG_SPECIFY_ERLINIT_CONF),y)
-define NERVES_CONFIG_INSTALL_ERLINIT
-	cp $(BR2_PACKAGE_NERVES_CONFIG_ERLINIT_CONF_PATH) $(TARGET_DIR)/etc/erlinit.config
-endef
-endif
-
 define NERVES_CONFIG_INSTALL_RELEASE
 	# Copy the release that starts the shell over to the target
 	rm -fr $(NERVES_CONFIG_ERLANG_RELEASE_DIR)
@@ -49,14 +36,13 @@ endef
 
 define NERVES_CONFIG_INSTALL_TARGET_CMDS
 	$(NERVES_CONFIG_INSTALL_RELEASE)
-	$(NERVES_CONFIG_INSTALL_ERLINIT)
 endef
 
 # This is tricky. We want the squashfs created by Buildroot to have everything
-# except for the OTP release. The squashfs tools can only append to filesystems,
-# so we'll want to append OTP releases frequently. If it were possible to modify
-# a squashfs after the fact, then we could skip this part, but this isn't possible
-# on non-Linux platforms (i.e. no fakeroot).
+# except for the OTP release. The squashfs tools can only append to
+# filesystems, so we'll want to append OTP releases frequently. If it were
+# possible to modify a squashfs after the fact, then we could skip this part,
+# but this isn't possible on non-Linux platforms (i.e. no fakeroot).
 ROOTFS_SQUASHFS_ARGS += -e srv
 
 $(eval $(generic-package))

package/nerves-config/relx.config.m4

@@ -1,3 +1,3 @@
 {include_erts, false}.
 {include_src, false}.
-{release, {nerves_config, "0.1.0"}, [APPS]}.
+{release, {nerves_config, "0.1.0"}, [stdlib, crypto]}.

package/nerves-config/vm.args.m4

@@ -1,10 +1,3 @@
-ifelse(DISTRIBUTION, `y', `
-## Name of the node
--sname SNAME
-
-## Cookie for distributed erlang
--setcookie COOKIE
-')
 ## Heartbeat management; auto-restarts VM if it dies or becomes unresponsive
 ## (Disabled by default..use with caution!)
 ##-heart