fix: Fixes #2464 Replace git use for finding project root. Dedicated dockerignore with .git/ for 277MB image

docker/README.md

@@ -1,6 +1,6 @@
 # Substrate Builder Docker Image
 
-The Docker image in this folder is a `builder` image. It is self contained and allow users to build the binaries themselves.
+The Docker image in this folder is a `builder` image. It is self contained and allows users to build the binaries themselves.
 There is no requirement on having Rust or any other toolchain installed but a working Docker environment.
 
 Unlike the `parity/polkadot` image which contains a single binary (`polkadot`!) used by default, the image in this folder builds and contains several binaries and you need to provide the name of the binary to be called.
@@ -12,6 +12,11 @@ You should refer to the .Dockerfile for the actual list. At the time of editing,
 - node-template
 - chain-spec-builder
 
+To generate the latest parity/substrate image. Please first run:
+```sh
+./build.sh
+```
+
 The image can be used by passing the selected binary followed by the appropriate tags for this binary.
 
 Your best guess to get started is to pass the `--help flag`. Here are a few examples:

docker/build.sh

@@ -3,9 +3,8 @@ set -e
 
 pushd .
 
-# The following line ensure we run from the project root
-PROJECT_ROOT=`git rev-parse --show-toplevel`
-cd $PROJECT_ROOT
+# Change to the project root and supports calls from symlinks
+cd $(dirname "$(dirname "$(realpath "${BASH_SOURCE[0]}")")")
 
 # Find the current version from Cargo.toml
 VERSION=`grep "^version" ./bin/node/cli/Cargo.toml | egrep -o "([0-9\.]+)"`
@@ -14,7 +13,7 @@ GITREPO=substrate
 
 # Build the image
 echo "Building ${GITUSER}/${GITREPO}:latest docker image, hang on!"
-time docker build -f ./docker/substrate_builder.Dockerfile -t ${GITUSER}/${GITREPO}:latest .
+time DOCKER_BUILDKIT=1 docker build -f ./docker/substrate_builder.Dockerfile -t ${GITUSER}/${GITREPO}:latest .
 docker tag ${GITUSER}/${GITREPO}:latest ${GITUSER}/${GITREPO}:v${VERSION}
 
 # Show the list of available images for this repo

docker/substrate_builder.Dockerfile

@@ -24,10 +24,10 @@ RUN useradd -m -u 1000 -U -s /bin/sh -d /substrate substrate && \
 	mkdir -p /data /substrate/.local/share/substrate && \
 	chown -R substrate:substrate /data && \
 	ln -s /data /substrate/.local/share/substrate && \
-# unclutter and minimize the attack surface
-	rm -rf /usr/bin /usr/sbin && \
 # Sanity checks
 	ldd /usr/local/bin/substrate && \
+# unclutter and minimize the attack surface
+	rm -rf /usr/bin /usr/sbin && \
 	/usr/local/bin/substrate --version
 
 USER substrate

docker/substrate_builder.Dockerfile.dockerignore

@@ -0,0 +1,11 @@
+doc
+**target*
+.idea/
+.git/
+.github/
+Dockerfile
+.dockerignore
+.local
+.env*
+HEADER-GPL3
+LICENSE-GPL3