[#226] Change error message formatting

[int-index]

Description

Problem: multiple issues with the CLI output

1. In the --help output, metavars GLOB_PATTERN and REPOSITORY_TYPE used spaces instead of underscores. Variables typically don't contain spaces in their names, so it looked confusing.
2. Incorrect or unintuitive coloring of the output. For example, filenames were dim even though they're important and should stand out, the report of success wasn't green, error messages weren't red, etc.
3. Excessive indentation and empty lines that made it difficult to visually parse the error report. Also the use of the exotic ➥ character that looks bad in many font configurations.
4. Filenames and line numbers were far apart, making it impossible to Ctrl+Click to jump to the source of the error.
5. In case of connection failure, the output was too verbose and platform-dependent.

Solution:

1. Adjust the pretty-printing functions and update test output.
2. Extend VerifyError with a constructor for connection failures.

Related issue(s)

Fixes #226.

✅ Checklist

Related changes (conditional)

• Tests

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from
    silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • README
    • Haddock

• Public contracts

  • Any modifications of public contracts comply with the Evolution
    of Public Contracts policy.
  • I added an entry to the changelog if my changes are visible to the users
    and
  • provided a migration guide for breaking changes if possible

Stylistic guide (mandatory)

• My commits comply with the policy used in Serokell.
• My code complies with the style guide.

✓ Release Checklist

• I updated the version number in package.yaml.
• I updated the changelog and moved everything
  under the "Unreleased" section to a new section for this release version.
• (After merging) I edited the auto-release.
  • Change the tag and title using the format vX.Y.Z.
  • Write a summary of all user-facing changes.
  • Deselect the "This is a pre-release" checkbox at the bottom.
• (After merging) I updated xrefcheck-action.
• (After merging) I uploaded the package to hackage.

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[gromakovsky]

Some changes look a bit subjective, but I can't say I'm strongly against anything, so let me approve. @Martoon-00 may review this week, let's give him a chance as well.

[Martoon-00]

Looks good, I see why these changes are reasonable and agree.

One concern: after merging error message for every single reference into one block, discrepancies in indentation became more apparent:

• The difference in leading - being present at one line and being absent at another. Maybe we can remove this - in lists after all. (Clearly the last line is not a list, but the difference still stands out)

check-images.md:20:1-34: bad reference:
  The reference to "bad image ref 3" failed verification.
  - link (relative): ./3.png      <------
  File does not exist:
    ./3.png                               <------

• Indentation size here:

The reference to "Reference lowered" failed verification.
  - anchor (file-local): uppercase-name
  Anchor 'uppercase-name' is not present, did you mean:
      - UPPERCASE-NAME (handmade) 14:3-27

Maybe these are worth changing to look uniform. WDYT?

[int-index]

Agreed, I'll try to change the phrasing further to avoid this issue.