Avoid exotic unicode symbols

[dcastro]

Clarification and motivation

We're using the following characters in xrefcheck's output:

1. ➥ (U+27A5): indicates a scanning/verification error.
2. ⛀ (U+26C0): indicates a verification error for a local link
3. ⛂ (U+26C2): indicates a verification error for an external link
4. ⮚ (U+2B9A): indicates a file in the repository (when xrefcheck is invoked with -v)

There are some problems with this:

• character (4) does not come a wide font support. Neither Ubuntu nor macOS come with any of the supported fonts, so the character won't be correcly rendered.
• characters (2) and (3) have a better font support, but still not good:
  • They're displayed correctly in Ubuntu. AFAIK, Ubuntu comes with the FreeSerif font.
  • But they're not displayed correctly in macOS, it doesn't come with any of the supported fonts.

(I haven't checked Windows support, we'll likely have issues there too.)

Given these problems, I think it's better to simply avoid using exotic unicode characters.
Let's use other visual cues instead (coloring, indentation, etc).

• I don't think we need characters (2) and (3). They're mainly used as a visual cue to distinguish between local and external links; but this distinction is already communicated via the Buildable LocationType in color.
• Character (4) doesn't seem to be needed either: we already use colors and indentation for this.
• Character (1) seems to have good support: Ubuntu via FreeSerif and macOS via Arial Unicode MS. I'm pretty sure it should also work on Windows out of the box, @Sorokin-Anton can you please double-check this?

Acceptance criteria

• We're no longer using characters 2/3/4 as visual cues
• If character 1 is supported on Windows out of the box, we leave it alone. Otherwise, let's decide what do about it.

[Sorokin-Anton]

(1) works on Windows in any terminal if proper codepage was used (and in #164 we're setting correct codepage). Others are displayed correctly only in VSCode terminal (t uses some nice font), so looks like they are not very popular

[aeqz]

(4) is being used as a bullet character in a list. Should we replace it with another character (e.g. -) or leave that kind of entries without a bullet character?

This is how it looks like without bullet character (README.md and docs/installation.md would be coloured although not visible here):

=== Repository data ===        

  README.md:
    - references:
      - reference (absolute) at src:3:1-64:
          - text: "installation document"
          - link: /docs/installation.md
          - anchor: installation-step
    - anchors:
          - xrefcheck-demo (header I) at src:1:1-16

  docs/installation.md:
    - references:
      - reference (external) at src:3:1-51:
          - text: "Markdown"
          - link: https://www.markdowntutorial.com/lssons
          - anchor: -
      - reference (relative) at src:7:1-18:
          - text: "Broken"
          - link: ./broken
          - anchor: -

And this is how it looks like with bullet character:

=== Repository data ===        

  - README.md:
    - references:
      - reference (absolute) at src:3:1-64:
          - text: "installation document"
          - link: /docs/installation.md
          - anchor: installation-step
    - anchors:
          - xrefcheck-demo (header I) at src:1:1-16

  - docs/installation.md:
    - references:
      - reference (external) at src:3:1-51:
          - text: "Markdown"
          - link: https://www.markdowntutorial.com/lssons
          - anchor: -
      - reference (relative) at src:7:1-18:
          - text: "Broken"
          - link: ./broken
          - anchor: -

[Martoon-00]

That's a good question.

To me, the version without the bullet characters looks cleaner and the visual ordering does not seem to be lost. But it's 7 vs 3 votes from my side, I don't have a strong preference.

What do you think about this case?

[aeqz]

I agree! The version without bullets looks nicer for me also.