Install a Bash Linter (#13)

* Install a bash linter

* Fix linter

* Add linter badge

.github/workflows/linter.yml

@@ -0,0 +1,12 @@
+name: Linter
+
+on: push
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v1
+      - name: Run Shellcheck
+        uses: azohra/shell-linter@latest

README.md

@@ -12,6 +12,8 @@
     This action helps you to sync your PRs with tasks in Teamwork to streamline team collaboration and your development workflows. 
 </p>
 
+![Linter](https://github.com/Teamwork/github-sync/workflows/Linter/badge.svg)
+
 ## Getting Started
 
 ### Prerequisites

entrypoint.sh

@@ -9,6 +9,7 @@ fi
 
 export PROJECT_HOME
 
+# shellcheck disable=SC1090
 source "$PROJECT_HOME/src/main.sh"
 
 main "$@"

src/main.sh

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
 
+# shellcheck disable=SC1090
 source "$PROJECT_HOME/src/ensure.sh"
 source "$PROJECT_HOME/src/github.sh"
 source "$PROJECT_HOME/src/misc.sh"
@@ -26,14 +27,14 @@ main() {
     exit 0
   fi
 
-  log::message "Task found with the id: "$task_id
+  log::message "Task found with the id: $task_id"
 
   export TEAMWORK_TASK_ID=$task_id
 
   local -r event=$(github::get_event_name)
   local -r action=$(github::get_action)
 
-  log::message "Event: " $event " - Action: " $action
+  log::message "Event: $event - Action: $action"
 
   if [ "$event" == "pull_request" ] && [ "$action" == "opened" ]; then
     teamwork::pull_request_opened

src/teamwork.sh

@@ -4,21 +4,21 @@ teamwork::get_task_id_from_body() {
   local -r body=$1
 
   pat='tasks\/[0-9]{1,}'
-  task=$(echo $body | grep -Eo $pat)
-  task_id=$(echo $task | tr -cd  '[[:digit:]]')
+  task=$(echo "$body" | grep -Eo "$pat")
+  task_id=$(echo "$task" | tr -cd  '[:digit:]')
 
-  echo $task_id
+  echo "$task_id"
 }
 
 teamwork::add_comment() {
   local -r body=$1
 
   response=$(curl -X "POST" "$TEAMWORK_URI/projects/api/v1/tasks/$TEAMWORK_TASK_ID/comments.json" \
-       -u $TEAMWORK_API_TOKEN':' \
+       -u "$TEAMWORK_API_TOKEN"':' \
        -H 'Content-Type: application/json; charset=utf-8' \
        -d "{ \"comment\": { \"body\": \"$body\", \"notify\": \"\", \"content-type\": \"text\", \"isprivate\": false } }" )
 
-  echo $response
+  echo "$response"
 }
 
 teamwork::pull_request_opened() {