update contribution notes

CONTRIBUTING.md

@@ -1,8 +1,30 @@
 # Contributing
 
+## Building locally
+
+```shell
+BUILD_TAG='my-monero-build' ./build.sh
+```
+
 ## Publishing a new release
 
-1) Checkout a new branch matching the release version to be built
 1) Update the `VERSION` file to match the release version to be built
-1) Commit and Push
-1) Checkout `master` and merge the created version branch
+
+1) Build
+
+1) Test
+
+1) Checkout a new branch and commit
+
+    ```shell
+    git checkout -b "$(< VERSION)"
+    git commit -m "bump to $(< VERSION)"
+    ```
+
+1) Push
+
+1) Wait for CI to validate builds
+
+1) Merge to `master`
+
+1) Push

build.sh

@@ -2,23 +2,25 @@
 
 set -eu
 
-if [ -n "${DEBUG:-}" ]; then
+if [[ -n "${DEBUG:+1}" ]]; then
 	set -x
 fi
 
-repo='monero-project/monero'
-tag="$(< VERSION)"
-sha="$(curl -LSs "https://api.github.com/repos/${repo}/git/ref/tags/${tag}" | jq -r '.object.sha')"
+version="$(< VERSION)"
+
+version_sha="$(curl -LSs "https://api.github.com/repos/monero-project/monero/git/ref/tags/${version}" | jq -r '.object.sha')"
 
-build_flags="${1:-}"
 build_date="$(date -u +'%Y-%m-%dT%H:%M:%SZ')"
+
+build_tag="${BUILD_TAG:-cornfeedhobo/monero:$version}"
+
 build_script="$(sed -e "s/[[:space:]]\+/ /g" <<-ENDSCRIPT
-	docker build ${build_flags} \
+	docker build ${@} \
 		--build-arg BUILD_DATE=${build_date} \
-		--build-arg MONERO_VERSION=${tag} \
-		--build-arg MONERO_HASH=${sha} \
+		--build-arg MONERO_VERSION=${version} \
+		--build-arg MONERO_HASH=${version_sha} \
 		--build-arg MONERO_TARGET=release \
-		-t cornfeedhobo/monero:${tag} .
+		-t ${build_tag} .
 ENDSCRIPT
 )"