JavaScript, YAML: wrapper around js-yaml that allows literal/folded styles on documents, eg. --- | or --- > without all that "crazy" indenting.

yaml-indent-documents.js

/*
 * yaml-indent-documents
 *
 * Copyright (c) 2012 "Cowboy" Ben Alman
 * Licensed under the MIT license.
 * http://benalman.com/about/license/
 */

'use strict';

var fs = require('fs');

var yaml = module.exports = require('js-yaml');

// Add one space of indentation to all documents starting with --- | or --- >
// because when writing TONS of content, indenting every line isn't practical.
//
// http://www.yaml.org/spec/1.2/spec.html#id2793652
// https://github.com/nodeca/js-yaml/issues/53
yaml.addIndents = function(src) {
  return String(src).split(/^(\-{3})/gm).map(function(s) {
    var m = s.match(/^(\s+[\|\^].*?\n)([\s\S]*?)\n$/);
    return m ? m[1] + m[2].replace(/^/gm, ' ') + '\n' : s;
  }).join('');
};

// This seems to do what I want it to.
yaml.parseDocs = function(src) {
  src = yaml.addIndents(src);
  var docs = [];
  yaml.loadAll(src, function(doc) {
    docs.push(doc);
  });
  return docs;
};

// So does this.
yaml.parseDocsFile = function(filepath) {
  return yaml.parseDocs(fs.readFileSync(filepath));
};

z-input.not-quite.yaml

---
a:
  When parsed, these lines
  SHOULD NOT retain linebreaks.
b: |
  When parsed, these lines
  SHOULD retain linebreaks
  and trailing newline.

c: |+
  When parsed, these lines
  SHOULD retain linebreaks
  and all trailing whitespace.

d: |-
  When parsed, these lines
  SHOULD retain linebreaks
  with no trailing whitespace.

# When writing TONS of content, indenting every line isn't practical.
---
When parsed, these lines
SHOULD NOT retain linebreaks.
--- |
When parsed, these lines
SHOULD retain linebreaks
and trailing newline.

--- |+
When parsed, these lines
SHOULD retain linebreaks
and all trailing whitespace.

--- |-
When parsed, these lines
SHOULD retain linebreaks
with no trailing whitespace.

z-output.json

[
  {
    "a": "When parsed, these lines SHOULD NOT retain linebreaks.",
    "b": "When parsed, these lines\nSHOULD retain linebreaks\nand trailing newline.\n",
    "c": "When parsed, these lines\nSHOULD retain linebreaks\nand all trailing whitespace.\n\n",
    "d": "When parsed, these lines\nSHOULD retain linebreaks\nwith no trailing whitespace."
  },
  "When parsed, these lines SHOULD NOT retain linebreaks.",
  "When parsed, these lines\nSHOULD retain linebreaks\nand trailing newline.\n",
  "When parsed, these lines\nSHOULD retain linebreaks\nand all trailing whitespace.\n\n",
  "When parsed, these lines\nSHOULD retain linebreaks\nwith no trailing whitespace."
]

As I just wrote in the issue, I believe it's a typo in the source documents, you can check my fork.