kernel: Drop 'kernel_' prefix from kernel config files

It's kinda obvious that these are kernel configuration files
and, looking at various other distros it seems more common
to call the files 'config-<foo>'.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

docs/kernels.md

@@ -87,7 +87,7 @@ contains an example for the configuration.
 Each series of kernels has a config file dedicated to it
 in [../kernel/](../kernel),
 e.g.
-[kernel.config-4.9.x-x86_64](../kernel/kernel_config-4.9.x-x86_64),
+[config-4.9.x-x86_64](../kernel/config-4.9.x-x86_64),
 which is applied during the kernel build process.
 
 If you need to modify the kernel config, `make kconfig` in
@@ -122,7 +122,7 @@ architectures to a minimum, so if you make changes to one
 configuration also try to apply it to the others. The script [kconfig-split.py](../scripts/kconfig-split.py) can be used to compare kernel config files. For example:
 
 ```sh
-../scripts/kconfig-split.py kernel_config-4.9.x-aarch64 kernel_config-4.9.x-x86_64
+../scripts/kconfig-split.py config-4.9.x-aarch64 config-4.9.x-x86_64
 ```
 
 creates a file with the common and the x86_64 and arm64 specific
@@ -165,7 +165,7 @@ The kernel build system has some provision to allow local
 customisation to the build.
 
 If you want to override/add some kernel config options, you can add a
-file called `kernel_config-foo` and then invoke the build with `make
+file called `config-foo` and then invoke the build with `make
 EXTRA=-foo build_4.9.x-foo` and this will build an image with the
 additional kernel config options enabled.
 

kernel/Dockerfile

@@ -78,13 +78,13 @@ RUN case $(uname -m) in \
         KERNEL_DEF_CONF=/linux/arch/arm64/configs/defconfig; \
         ;; \
     esac  && \
-    cp /kernel_config-${KERNEL_SERIES}-$(uname -m) ${KERNEL_DEF_CONF}; \
+    cp /config-${KERNEL_SERIES}-$(uname -m) ${KERNEL_DEF_CONF}; \
     if [ -n "${EXTRA}" ]; then \
         sed -i "s/CONFIG_LOCALVERSION=\"-linuxkit\"/CONFIG_LOCALVERSION=\"-linuxkit${EXTRA}\"/" ${KERNEL_DEF_CONF}; \
         if [ "${EXTRA}" = "-dbg" ]; then \
             sed -i 's/CONFIG_PANIC_ON_OOPS=y/# CONFIG_PANIC_ON_OOPS is not set/' ${KERNEL_DEF_CONF}; \
         fi && \
-        cat /kernel_config${EXTRA} >> ${KERNEL_DEF_CONF}; \
+        cat /config${EXTRA} >> ${KERNEL_DEF_CONF}; \
     fi && \
     make defconfig && \
     make oldconfig && \

kernel/Dockerfile.kconfig

@@ -32,8 +32,8 @@ RUN for VERSION in ${KERNEL_VERSIONS}; do \
                    patch -p1 < "$patch"; \
                done; \
             fi && \
-        mv /kernel_config-${SERIES}-x86_64 arch/x86/configs/x86_64_defconfig && \
+        mv /config-${SERIES}-x86_64 arch/x86/configs/x86_64_defconfig && \
-        mv /kernel_config-${SERIES}-aarch64 arch/arm64/configs/defconfig; \
+        mv /config-${SERIES}-aarch64 arch/arm64/configs/defconfig; \
     done
 
 ENTRYPOINT ["/bin/sh"]

kernel/Makefile

@@ -19,7 +19,7 @@ IMAGE_PERF:=kernel-perf
 IMAGE_ZFS:=zfs-kmod
 
 # You can specify an extra options for the Makefile. This will:
-# - append a kernel_config$(EXTRA) to the kernel config for your kernel/arch
+# - append a config$(EXTRA) to the kernel config for your kernel/arch
 # - append $(EXTRA) to the CONFIG_LOCALVERSION of your kernel
 EXTRA?=
 
@@ -93,7 +93,7 @@ sources/linux-$(1).tar.xz: Makefile | sources
 KERNEL_VERSIONS+=$(1)
 endif
 
-build_$(2)$(3): Dockerfile Makefile $(wildcard patches-$(2)/*) $(wildcard kernel_config-$(2)*) kernel_config-dbg | sources
+build_$(2)$(3): Dockerfile Makefile $(wildcard patches-$(2)/*) $(wildcard config-$(2)*) config-dbg | sources
 	docker pull $(ORG)/$(IMAGE):$(1)$(3)-$(TAG)$(SUFFIX) || \
 		docker build \
 			--build-arg KERNEL_VERSION=$(1) \