Remove excessive empty lines from output

[dcastro]

Clarification and motivation

The output of xrefcheck seems to contain an excessive amount of empty lines.

Let's trim this.

Example 1

File a.md:

[a](invalid.md)
[a](invalid.md)

Output

$ xrefcheck
Configuration file not found, using default config for GitHub repositories

                                                                                                                                                    

=== Invalid references found ===

  ➥  In file a.md
    bad reference (relative) at src:1:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
  ➥  In file a.md
    bad reference (relative) at src:2:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
Invalid references dumped, 2 in total.

• We begin by printing Configuration file not found ... and an empty line to stderr, and then 2 empty lines to stdout. These 2 lines are really not needed.
• We print 2 lines after each invalid reference - 1 line would suffice.

Example 2

If we add an empty b.md file and run xrefcheck with -v:

File a.md:

[a](invalid.md)
[a](invalid.md)

File b.md:

Output

$ xrefcheck -v
Configuration file not found, using default config for GitHub repositories

=== Repository data ===        

  ⮚ a.md:
    - references:
        - reference (relative) at src:1:1-15:
            - text: "a"
            - link: invalid.md
            - anchor: -
        - reference (relative) at src:2:1-15:
            - text: "a"
            - link: invalid.md
            - anchor: -
    - anchors: []
    
  ⮚ b.md:
    - references:
        - reference (relative) at src:1:1-9:
            - text: "a"
            - link: a.md
            - anchor: -
        - reference (relative) at src:2:1-9:
            - text: "a"
            - link: a.md
            - anchor: -
    - anchors: []
    

                                                                                                                                                    

=== Invalid references found ===

  ➥  In file a.md
    bad reference (relative) at src:1:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
  ➥  In file a.md
    bad reference (relative) at src:2:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
Invalid references dumped, 2 in total.

• "Repository data" only prints 1 empty line in-between each item, which is good.
• However, we now have 4 empty lines before the "Invalid references" section.

Example 3

Now let's try printing scanning errors:

File a.md:

<!-- xrefcheck: ignore wrong -->
<!-- xrefcheck: ignore wrong -->

[a](invalid.md)
[a](invalid.md)

File b.md:

Output

$ xrefcheck -v
Configuration file not found, using default config for GitHub repositories

=== Repository data ===        

  ⮚ a.md:
    - references:
        - reference (relative) at src:4:1-15:
            - text: "a"
            - link: invalid.md
            - anchor: -
        - reference (relative) at src:5:1-15:
            - text: "a"
            - link: invalid.md
            - anchor: -
    - anchors: []
    
  ⮚ b.md:
    - references:
        - reference (relative) at src:1:1-9:
            - text: "a"
            - link: a.md
            - anchor: -
        - reference (relative) at src:2:1-9:
            - text: "a"
            - link: a.md
            - anchor: -
    - anchors: []
    

=== Scan errors found ===

  ➥  In file a.md
    scan error at src:1:1-32:
    
    ⛀  Unrecognised option "wrong" perhaps you meant <"ignore link"|"ignore paragraph"|"ignore all">
    
    
  ➥  In file a.md
    scan error at src:2:1-32:
    
    ⛀  Unrecognised option "wrong" perhaps you meant <"ignore link"|"ignore paragraph"|"ignore all">
    
    
Scan errors dumped, 2 in total.
                                                                                                                                                    

=== Invalid references found ===

  ➥  In file a.md
    bad reference (relative) at src:4:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
  ➥  In file a.md
    bad reference (relative) at src:5:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
Invalid references dumped, 2 in total.

• Again, similar issues as we saw in example 1. We're printing 2 lines after each scanning error, 1 would suffice.
• We're also printing 2 empty lines after "Scan errors dumped, 2 in total."

Example 4

For some reason, the buildable instance for the verification error ExternalResourceSomeError prints 1 additional empty line when compared to the other verification errors:

File a.md:

[a](http://wwwwwwwwwww)
[a](invalid.md)

Output

$ xrefcheck
xrefcheck   
Configuration file not found, using default config for GitHub repositories

                                                                                                                                                                      

=== Invalid references found ===

  ➥  In file a.md
    bad reference (external) at src:1:1-23:
      - text: "a"
      - link: http://wwwwwwwwwww
      - anchor: -
    
    ⛂  ConnectionFailure Network.Socket.getAddrInfo (called with preferred socket type/protocol: AddrInfo {addrFlags = [], addrFamily = AF_UNSPEC, addrSocketType = Stream, addrProtocol = 0, addrAddress = 0.0.0.0:0, addrCanonName = Nothing}, host name: Just "wwwwwwwwwww", service name: Just "80"): does not exist (Temporary failure in name resolution)
    
    
    
  ➥  In file a.md
    bad reference (relative) at src:2:1-15:
      - text: "a"
      - link: invalid.md
      - anchor: -
    
    ⛀  File does not exist:
        invalid.md
    
    
Invalid references dumped, 2 in total.

As we can see, there's 3 empty lines after ConnectionFailure.

Acceptance criteria

• We never print 2 adjacent empty lines.