asciidocext: The output destination directory is url escaped and the image is not displayed.

[szk302]

What version of Hugo are you using (hugo version)?

$ hugo version 
Hugo Static Site Generator v0.80.0-792EF0F4/extended linux/amd64 BuildDate: 2020-12-31T13:46:18Z

Does this issue reproduce with the latest release?

Yes

• PlantumlをHugoで表示する.adoc

= PlantumlをHugoで表示する

[source,plantuml]
----
@startuml
A1 - B1
A1 -- C2
A1 -- D2
C2 - E2
@enduml
----

[plantuml]
----
@startuml
A1 - B1
A1 -- C2
A1 -- D2
C2 - E2
@enduml
----

markup:
  asciidocext:
    extensions:
      - asciidoctor-html5s
      - asciidoctor-diagram
    workingFolderCurrent: true
    trace: true
    attributes:
      my-base-url: 'https://localhost/'
      my-attribute-name: my value

• hugo --destination output

~
├── posts
│   ├── Plantuml%E3%82%92Hugo%E3%81%A7%E8%A1%A8%E7%A4%BA%E3%81%99%E3%82%8B
│   │   └── diag-44963d5c8fb0ea5d64d7c880e7bfa7fe.png
│   ├── PlantumlをHugoで表示する
│   │   └── index.html
│   ├── index.html
│   ├── index.xml
│   └── page
│       └── 1
│           └── index.html
~