Gradle: replace build with shadowJar plugin (#68)

Gradle build compiles our source files and libraries used in the
program into separate jar files, and delivers the entire package as
a zip file.

It is rather inconvenient as user would have to extract from the zip
file to use it and also have more unnecessary files to deal with.
Additionally, if we package only our own class files into the JAR
file, it will not work properly unless the user has all the other 
JAR files (i.e. third party libraries) our classes depend on.

Let's replace the gradle build with shadowJar plugin to package all
dependencies into a single JAR file which enhance usability and
portability.

Author: eugenepeh

build.gradle

@@ -1,9 +1,9 @@
 plugins {
     id 'java'
     id 'checkstyle'
+    id 'com.github.johnrengelman.shadow' version '2.0.3'
     id 'application'
 }
-
 mainClassName = "frontend.RepoSense"
 
 repositories {
@@ -26,10 +26,9 @@ dependencies {
     compile group: 'org.json', name: 'json', version: '20180130'
 }
 
-jar {
-    manifest {
-        attributes 'Main-Class': 'frontend.RepoSense'
-    }
+shadowJar {
+    archiveName = 'RepoSense.jar'
+    destinationDir = file("${buildDir}/jar/")
 }
 
 task myZip(type: Zip) {
@@ -38,10 +37,9 @@ task myZip(type: Zip) {
     destinationDir = file("src/main/resources")
 }
 
-tasks.build.dependsOn("myZip");
+tasks.shadowJar.dependsOn("myZip");
 tasks.run.dependsOn("myZip");
 
-
 configurations {
   functionalCompile.extendsFrom testCompile
   functionalRuntime.extendsFrom testRuntime

docs/Build.md

@@ -0,0 +1,11 @@
+# Build from Source
+
+This guide explains how to compile the executable Jar.
+
+1. Download our source code by
+   * using Git clone <br>
+     e.g. `git clone https://github.com/reposense/RepoSense.git` <br>
+   * or download and extract our [zip file](https://github.com/reposense/RepoSense/archive/master.zip).
+2. In the `RepoSense` directory, execute the below command in the terminal <br>
+   `gradlew shadowJar`
+3. The executable Jar file will be generated in the folder `build` > `jar` with the name `RepoSense.jar` upon successful build.

docs/user_guide.md

@@ -5,16 +5,21 @@
 4. Profit!
 
 ## Dependencies
-1. Git
-2. Gradle
+1. **JDK `1.8.0_60`**  or later
+   * This app only works with Java 8 version.
+2. **Git** on the command line
+   * Ensure that you're able to use it on the OS terminal.
+
 ## How to Generate Dashboard
-```sh
-$ gradle clean build
-```
-Unzip the file in build/distributions/
+1. Download the latest executable Jar on our [release](https://github.com/reposense/RepoSense/releases/latest).
+   * Alternatively, you can compile the executable Jar yourself by following our [build from source guide](Build.md).
+2. Execute it on the OS terminal. <br>
+Usage: `java -jar RepoSense.jar -config CSV_CONFIG_FILE_PATH [-output OUTPUT_DIRECTORY] [-since DD/MM/YYYY] [-until DD/MM/YYYY]`
+3. The dashboard can be in the folder designated in OUTPUT_DIRECTORY, or current working directory otherwise, as index.html.
+
+Sample usage:
 ```
-$ cd build/distributions/RepoSense/bin
-$ ./RepoSense -config CSV_path.csv -output output_path/ -since 01/10/2017 -until 01/11/2017
+$ java -jar RepoSense.jar -config CSV_path.csv -output output_path/ -since 01/10/2017 -until 01/11/2017
 ```
 Argument List:
 - config: Mandatory. The path to the CSV config file.