Refactor makefile script

* Fix shellcheck issues
* Fix some shell style inconsistencies.
* Split out some functions.

Signed-off-by: Ben Kochie <superq@gmail.com>

scripts/sync_makefiles.sh

@@ -1,5 +1,5 @@
-#!/bin/bash
-
+#!/usr/bin/env bash
+# vim: ts=2 et
 # Setting -x is absolutely forbidden as it could leak the GitHub token.
 set -uo pipefail
 
@@ -15,59 +15,84 @@ orgs="prometheus prometheus-community"
 
 GITHUB_TOKEN="${GITHUB_TOKEN:-}"
 if [ -z "${GITHUB_TOKEN}" ]; then
-	echo -e "\e[31mGitHub token (GITHUB_TOKEN) not set. Terminating.\e[0m"
-	exit 1
+  echo -e "\e[31mGitHub token (GITHUB_TOKEN) not set. Terminating.\e[0m"
+  exit 1
 fi
 
 # Go to the root of the repo
-cd "$(git rev-parse --show-cdup)"
+cd "$(git rev-parse --show-cdup)" || exit 1
 
 source_makefile="$(pwd)/Makefile.common"
 source_checksum="$(sha256sum Makefile.common | cut -d' ' -f1)"
 
-tmp_dir=$(mktemp -d)
-trap "rm -rf ${tmp_dir}" EXIT
+tmp_dir="$(mktemp -d)"
+trap 'rm -rf "${tmp_dir}"' EXIT
+
+fetch_repos() {
+  local url="https://api.github.com/users/${1}/repos?per_page=100"
+  curl --retry 5 --silent -u "${git_user}:${GITHUB_TOKEN}" "${url}" 2>/dev/null |
+    jq -r '.[] | select( .name != "prometheus" ) | .name'
+}
+
+push_branch() {
+  # stdout and stderr are redirected to /dev/null otherwise git-push could leak
+  # the token in the logs.
+  git push --quiet \
+    "https://${GITHUB_TOKEN}:@github.com/${1}" \
+    --set-upstream "${branch}" 1>/dev/null 2>&1
+}
+
+post_template='{"title":"%s","base":"master","head":"%s","body":"%s"}'
+post_json="$(printf "${post_template}" "${pr_title}" "${branch}" "${pr_msg}")"
+post_pull_request() {
+  curl --show-error --silent --fail \
+    -u "${git_user}:${GITHUB_TOKEN}" \
+    -d "${post_json}" \
+    "https://api.github.com/repos/${1}/pulls"
+}
+
+process_repo() {
+  local org_repo="$1"
+  echo -e "\e[32mAnalyzing '${org_repo}'\e[0m"
 
-for org in $orgs
-do
-	# Iterate over all repositories in ${org}. The GitHub API can return 100 items
-	# at most but it should be enough for us as there are less than 40 repositories
-	# currently.
-	curl --retry 5 --silent -u "${git_user}:${GITHUB_TOKEN}" https://api.github.com/users/${org}/repos?per_page=100 2>/dev/null | jq -r '.[] | select( .name != "prometheus" ) | .name' | while read -r; do
-		repo="${REPLY}"
-		echo -e "\e[32mAnalyzing '${repo}'\e[0m"
+  target_makefile="$(curl -s --fail "https://raw.githubusercontent.com/${org_repo}/master/Makefile.common")"
+  if [ -z "${target_makefile}" ]; then
+    echo "Makefile.common doesn't exist in ${org_repo}"
+    return
+  fi
+  target_checksum="$(echo "${target_makefile}" | sha256sum | cut -d' ' -f1)"
+  if [ "${source_checksum}" == "${target_checksum}" ]; then
+    echo "Makefile.common is already in sync."
+    return
+  fi
 
-		target_makefile="$(curl -s --fail "https://raw.githubusercontent.com/${org}/${repo}/master/Makefile.common")"
-		if [ -z "${target_makefile}" ]; then
-			echo "Makefile.common doesn't exist in ${repo}"
-			continue
-		fi
-		target_checksum="$(echo ${target_makefile} | sha256sum | cut -d' ' -f1)"
-		if [ "${source_checksum}" == "${target_checksum}" ]; then
-			echo "Makefile.common is already in sync."
-			continue
-		fi
+  # Clone target repo to temporary directory and checkout to new branch
+  git clone --quiet "https://github.com/${org_repo}.git" "${tmp_dir}/${org_repo}"
+  cd "${tmp_dir}/${org_repo}" || return 1
+  git checkout -b "${branch}" || return 1
 
-		# Clone target repo to temporary directory and checkout to new branch
-		git clone --quiet "https://github.com/${org}/${repo}.git" "${tmp_dir}/${repo}"
-		cd "${tmp_dir}/${repo}"
-		git checkout -b "${branch}"
+  # Replace Makefile.common in target repo by one from prometheus/prometheus
+  cp -f "${source_makefile}" ./
+  if [ -n "$(git status --porcelain)" ]; then
+    git config user.email "${git_mail}"
+    git config user.name "${git_user}"
+    git add .
+    git commit -s -m "${commit_msg}"
+    if push_branch "${org_repo}"; then
+      post_pull_request "${org_repo}"
+    fi
+  fi
+}
 
-		# Replace Makefile.common in target repo by one from prometheus/prometheus
-		cp -f "${source_makefile}" ./
-		if [ -n "$(git status --porcelain)" ]; then
-			git config user.email "${git_mail}"
-			git config user.name "${git_user}"
-			git add .
-			git commit -s -m "${commit_msg}"
-			# stdout and stderr are redirected to /dev/null otherwise git-push could leak the token in the logs.
-			if git push --quiet "https://${GITHUB_TOKEN}:@github.com/${org}/${repo}" --set-upstream "${branch}" 1>/dev/null 2>&1; then
-				curl --show-error --silent \
-					-u "${git_user}:${GITHUB_TOKEN}" \
-					-X POST \
-					-d "{\"title\":\"${pr_title}\",\"base\":\"master\",\"head\":\"${branch}\",\"body\":\"${pr_msg}\"}" \
-					"https://api.github.com/repos/${org}/${repo}/pulls"
-			fi
-		fi
-	done
+for org in ${orgs}; do
+  mkdir -p "${tmp_dir}/${org}"
+  # Iterate over all repositories in ${org}. The GitHub API can return 100 items
+  # at most but it should be enough for us as there are less than 40 repositories
+  # currently.
+  fetch_repos "${org}" | while read -r repo; do
+    if ! process_repo "${org}/${repo}"; then
+      echo "Failed to process '${org}/${repo}'"
+      exit 1
+    fi
+  done
 done