1. Detail of the problem

After I clone a permission (e.g. Select) from a role to another role in hasura web console, and then trying to run npx hasura --project ./migrate migrate apply --down 1 to undo changes in the db schema.
I get error like this:

> npx hasura --project ./migrate migrate apply --down 1
time="2020-02-29T23:38:00+08:00" level=fatal msg="apply failed: [unexpected] postgres query error ($.args[1].args)\r\nFile: '1582990072304_apply_same_permissions_public_table_schoolRankings\\down.yaml'\r\n{\n    \"permission\": {\n        \"allow_aggregations\": false,\n        \"columns\": [\n     
       \"isActive\",\n            \"ARWURanking\",\n            \"id\",\n            \"QSRanking\",\n            \"school_id\",\n            \"THERanking\",\n            \"year\",\n            \"url\",\n            \"created_at\",\n            \"updated_at\"\n        ],\n        \"computed_fields\": [],\n        \"filter\": {}\n    },\n    \"role\": \"anonymous_role\",\n    \"table\": {\n        \"name\": \"schoolRankings\",\n        \"schema\": 
\"public\"\n    }\n}\r\n[23505] FatalError: duplicate key value violates unique constraint \"hdb_permission_pkey\"\r\nDescription: Key (table_schema, 
table_name, role_name, perm_type)=(public, schoolRankings, anonymous_role, select) already exists." 

And content of \migrations\1582990072304_apply_same_permissions_public_table_schoolRankings\down.yaml is:

- args:
    role: user
    table:
      name: schoolRankings
      schema: public
  type: drop_select_permission
- args:
    permission:
      allow_aggregations: false
      columns:
      - isActive
      - ARWURanking
      - id
      - QSRanking
      - school_id
      - THERanking
      - year
      - url
      - created_at
      - updated_at
      computed_fields: []
      filter: {}
    role: anonymous_role
    table:
      name: schoolRankings
      schema: public
  type: create_select_permission
- args:
    role: anonymous_role
    table:
      name: schoolRankings
      schema: public
  type: drop_select_permission

Then, I have manually removed last 2 items in down.yaml and up.yaml and run npx hasura --project ./migrate migrate apply --down 1 and npx hasura --project ./migrate migrate apply --up 1 without error.

2. How to replicate the issue

My hasura version is 1.1 and I use Docker Desktop for Windows to run it on my laptop.
My postgres version is PostgreSQL 9.5.19 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0 20160609, 64-bit running on windows wsl.

After cloned a permission to another role in console, /migrations folder should has a new migration folder of that change. It has a down.yaml file and its second item should be trying to create a new record but another record of the same (table_schema,
table_name, role_name, perm_type) already exists.

3. Expected behavior

When we clone a permission from role A to role B. The migration should not change permission of role A.