diffRefs API has type, diff_type params but uses only type

[arielshaqed]

diffRefs defines both:

• a "type" parameter, an unrestricted string;
• a "diff_type" parameter, a string enum of two_dot and three_dot.

But it ignores diff_type and uses only type, which should take one of the
enum values supposedly checked on diff_type.

diffRefs Swagger definition

  /repositories/{repository}/refs/{leftRef}/diff/{rightRef}:
    parameters:
      - in: path
        name: repository
        required: true
        schema:
          type: string
      - in: path
        name: leftRef
        required: true
        schema:
          type: string
        description: a reference (could be either a branch or a commit ID)
      - in: path
        name: rightRef
        required: true
        schema:
          type: string
        description: a reference (could be either a branch or a commit ID) to compare against
      - $ref: "#/components/parameters/PaginationAfter"
      - $ref: "#/components/parameters/PaginationAmount"
      - $ref: "#/components/parameters/PaginationPrefix"
      - $ref: "#/components/parameters/PaginationDelimiter"
      - in: query
        name: type
        schema:
          type: string
      - in: query
        name: diff_type
        schema:
          type: string
          enum: [two_dot, three_dot]
          default: three_dot

    get:
      tags:
        - refs
      operationId: diffRefs
      summary: diff references
      responses:
        200:
          description: diff between refs
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/DiffList"
        401:
          $ref: "#/components/responses/Unauthorized"
        404:
          $ref: "#/components/responses/NotFound"
        default:
          $ref: "#/components/responses/ServerError"