Why does snapcraft copy my home directory?

snapcraft
3 
name: gosim
version: "0.20"
summary: Block diagram simulator, like simulink
description: GoSim is a block diagram simulator similar to Simulink. Is uses GNU Octave as a mathematical engine. 
grade: stable
confinement: devmode
apps:
  gosim:
    command: java -jar $SNAP/GoSim/gosim.jar
parts:
  gosim:
    plugin: gradle
    source: .
    override-build: |
      export JAVA_HOME="/usr/lib/jvm/java-8-openjdk-amd64"
      gradle release -x test -x createGitTag
      unzip /home/cr/Skrivbord/Nymapp/GoSim.zip -d $SNAPCRAFT_PART_INSTALL/
    build-packages:
      - unzip
      - openjdk-8-jdk

it’s just a dot, i copied your example: https://docs.snapcraft.io/java-applications/7819

if it is a java jar file why are the source files needed? Can i just omit the line?

my snap isn’t working btw, i get an error:

thanks in advance