Rename Dockerfile.arm to Dockerfile.armhf to more clearly reflect the specific subversion of ARM it targets

Also, fix up some minor whitespace consistency issues, remove a little cruft, and update GOARM for armhf to 7 so that we're explicit.

Signed-off-by: Andrew "Tianon" Page <admwiggin@gmail.com>

Dockerfile.armhf

@@ -1,9 +1,9 @@
-# This file describes the standard way to build Docker on ARM, using docker
+# This file describes the standard way to build Docker on ARMv7, using docker
 #
 # Usage:
 #
 # # Assemble the full dev environment. This is slow the first time.
-# docker build -t docker -f Dockerfile.arm .
+# docker build -t docker -f Dockerfile.armhf .
 #
 # # Mount your source in an interactive container for quick testing:
 # docker run -v `pwd`:/go/src/github.com/docker/docker --privileged -i -t docker bash
@@ -70,22 +70,21 @@ RUN cd /usr/local/lvm2 \
 
 # Install Go
 ENV GO_VERSION 1.4.3
-RUN curl -sSL https://golang.org/dl/go${GO_VERSION}.src.tar.gz | tar -v -C /usr/local -xz \
-	&& mkdir -p /go/bin
+# TODO update GO_TOOLS_COMMIT below when this updates to 1.5+
+RUN curl -fsSL https://golang.org/dl/go${GO_VERSION}.src.tar.gz | tar -v -C /usr/local -xz
 ENV PATH /go/bin:/usr/local/go/bin:$PATH
 ENV GOPATH /go:/go/src/github.com/docker/docker/vendor
-# (set an explicit GOARM of 5 for maximum compatibility)
-ENV GOARM 5
-RUN cd /usr/local/go/src && ./make.bash --no-clean 2>&1
 
-# Compile Go for cross compilation
-ENV DOCKER_CROSSPLATFORMS " "
+# we're building for armhf, which is ARMv7, so let's be explicit about that
+ENV GOARM 7
+
+RUN cd /usr/local/go/src && ./make.bash --no-clean 2>&1
 
 # This has been commented out and kept as reference because we don't support compiling with older Go anymore.
 # ENV GOFMT_VERSION 1.3.3
 # RUN curl -sSL https://storage.googleapis.com/golang/go${GOFMT_VERSION}.$(go env GOOS)-$(go env GOARCH).tar.gz | tar -C /go/bin -xz --strip-components=2 go/bin/gofmt
 
-# Update this sha when we upgrade to go 1.5.0
+# TODO update this sha when we upgrade to Go 1.5+
 ENV GO_TOOLS_COMMIT 069d2f3bcb68257b627205f0486d6cc69a231ff9
 # Grab Go's cover tool for dead-simple code coverage testing
 # Grab Go's vet tool for examining go code to find suspicious constructs

Makefile

@@ -6,7 +6,7 @@ DOCKER_ENGINE_OSARCH = $(shell docker version | grep 'OS/Arch' | tail -1 | cut -
 DOCKER_FILE = Dockerfile
 # switch to different Dockerfile for linux/arm
 ifeq ($(DOCKER_ENGINE_OSARCH),linux/arm)
-  DOCKER_FILE = Dockerfile.arm
+	DOCKER_FILE = Dockerfile.armhf
 endif
 export DOCKER_FILE