[Elasticsearch] Elasticsearch 7.6 IDEA source code environment construction

1 Overview

1.1 Software environment

Intellij idea:2019.3
Gradle gradle-6.3-all.zip
JDK 12.0.2
macOS 10.15.4

1.2 Attention

1. Source code compilation environment for elasticsearch version 7.6, gradle version 5.5 and above, JDK 13 and above.
2. The source code version of es and the hairstyle version must be the same, because you need to configure the config and modules of es when you run the source code. You can use the release version directly here.
3. Specific