public Path getSourceFile() {
    return sourceFile;
  }
Gets the source file. The source file may be relative or absolute, so the caller should use
{@code getSourceFile().toAbsolutePath().toString()} for the serialized form since the
serialization could change independently of the path representation.

@return the source file
jib-build-plan/src/main/java/com/google/cloud/tools/jib/api/buildplan/FileEntry.java