Move and fix oncall.sh script (#18217)

In the future we can create automation to send reminders to a Slack
channel. Or send the list every time there's a oncall changeover.

tools/oncall/README.md

@@ -0,0 +1,8 @@
+# Oncall
+
+You can use the `oncall.sh` script to find out if there are any open issues or PRs from the community:
+```sh
+gh auth login
+./tools/oncall/oncall.sh issues
+./tools/oncall/oncall.sh prs
+```

tools/oncall/oncall.sh

@@ -0,0 +1,75 @@
+#!/usr/bin/env bash
+# Script for on-call use.
+# Formatted with shfmt. See https://github.com/mvdan/sh
+
+set -euo pipefail
+
+usage() {
+	cat <<EOF
+Contains useful commands for on-call.
+
+Usage:
+    $(basename "$0") <command>
+
+Commands:
+    issues  List open issues from outside contributors.
+    prs     List open prs from outside contributors.
+EOF
+}
+
+require() {
+	type "$1" >/dev/null 2>&1 || {
+		echo "$1 is required but not installed. Aborting." >&2
+		exit 1
+	}
+}
+
+issues() {
+	require gh
+	require jq
+
+	auth_status="$(gh auth status -t 2>&1)"
+	username="$(echo "${auth_status}" | sed -n -r 's/^.* Logged in to github.com account ([^[:space:]]+).*/\1/p')"
+	token="$(echo "${auth_status}" | sed -n -r 's/^.*Token: ([a-zA-Z0-9_]*)/\1/p')"
+
+	members="$(curl -s -u "${username}:${token}" https://api.github.com/orgs/fleetdm/members?per_page=100 | jq -r 'map(.login)')"
+
+	gh issue list --repo fleetdm/fleet --json id,title,author,url,createdAt,labels --limit 100 |
+		jq -r --argjson members "$members" \
+			'map(select(.author.login as $in | $members | index($in) | not)) | sort_by(.createdAt) | reverse'
+}
+
+prs() {
+	require gh
+	require jq
+
+	auth_status="$(gh auth status -t 2>&1)"
+	username="$(echo "${auth_status}" | sed -n -r 's/^.* Logged in to github.com account ([^[:space:]]+).*/\1/p')"
+	token="$(echo "${auth_status}" | sed -n -r 's/^.*Token: ([a-zA-Z0-9_]*)/\1/p')"
+
+	members="$(curl -s -u "${username}:${token}" https://api.github.com/orgs/fleetdm/members?per_page=100 | jq -r 'map(.login)' | jq '. += ["app/dependabot"]')"
+
+	# defaults to listing open prs
+	gh pr list --repo fleetdm/fleet --json id,title,author,url,createdAt |
+		jq -r --argjson members "$members" \
+			'map(select(.author.login as $in | $members | index($in) | not)) | sort_by(.createdAt) | reverse'
+}
+
+# main script
+case "$1" in
+issues)
+	issues
+	;;
+prs)
+	prs
+	;;
+-h | --help)
+	usage
+	exit 0
+	;;
+*)
+	echo "Invalid argument: $1"
+	usage
+	exit 1
+	;;
+esac