Adding update-geth target (#673)

Makefile

@@ -174,6 +174,9 @@ dep-ensure: ##@dependencies Dep ensure and apply all patches
 dep-install: ##@dependencies Install vendoring tool
 	go get -u github.com/golang/dep/cmd/dep
 
+update-geth: ##@dependencies Update geth (use GETH_BRANCH to optionally set the geth branch name)
+	./_assets/ci/update-geth.sh $(GETH_BRANCH)
+
 patch: ##@patching Revert and apply all patches
 	./_assets/patches/patcher
 

_assets/ci/update-geth.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+# This script updates the go-ethereum dependency, optionally updating the branch if GETH_BRANCH is provided.
+# If any changes were made, they will be committed.
+
+# Exit early if any errors are encountered
+set -e
+if [ ! -z "$GETH_BRANCH" ]; then
+	# escape slashes
+	GETH_BRANCH=$(echo $GETH_BRANCH | sed 's@\/@\\\/@g')
+	# Update go-ethereum contraint branch
+	sed -i 'N;N;s@\(\[\[constraint]]\n  name = "github.com\/ethereum\/go-ethereum"\n  branch =\)\(.*\)@\1 '"\"${GETH_BRANCH}\""'@g' Gopkg.toml
+fi
+dep ensure -v -update github.com/ethereum/go-ethereum
+if ! make dep-ensure; then
+    echo "Please fix patches and rerun. (dep-ensure failed)"
+    exit 1
+fi
+
+
+git add Gopkg.lock Gopkg.toml vendor/ _assets/patches/
+if $(git diff --cached --quiet); then
+	echo "No changes to commit. Geth up to date."
+    exit 0
+fi
+git commit --quiet -m "Updating Geth"
+echo "Geth updated."

_assets/docs/DEPENDENCIES.md

@@ -49,12 +49,7 @@ file is changed, `dep ensure` will re-generate `Gopkg.lock` as well.
 
 ## Updating `Geth`
 
-1. (for major releases) Update the branch name in `Gopkg.toml`.
-2. Update the `go-ethereum` dependency: `dep ensure -v -update github.com/ethereum/go-ethereum`.
-3. Update vendor files in `status-go`, and apply patches by running `make dep-ensure`.
-4. Commit patches.
-5. Commit `Gopkg.lock`, `Gopkg.toml` and `vendor` directories.
-
+Use the `update-geth` make target. For major releases, provide the GETH_BRANCH parameter. (e.g. `make update-geth GETH_BRANCH=release/1.9`). If there were any changes made, they will be committed while running this target.
 
 ## Commiting changes