Lua-YAML prettier multiline output

Option: yaml_pretty_multiline

The lua-yaml encoder selects the string style automatically, but in Tarantool context, it can be beneficial to enforce them, for example, for better readability. The yaml_pretty_multiline compat option allows to encode multiline strings in a block style.

The compat module allows you to chose between the lua-yaml encodes multiline strings as usual or in the enforced block scalar style:

 
tarantool> compat.yaml_pretty_multiline = 'old'---...tarantool> return "Title: xxx\n- Item 1\n- Item 2\n"---- 'Title: xxx  - Item 1  - Item 2  '...tarantool> compat.yaml_pretty_multiline = 'new'---...tarantool> return "Title: xxx\n- Item 1\n- Item 2\n"---- |  Title: xxx  - Item 1  - Item 2...

You can select the new/old behavior in compat. It affects the global YAML encoder.

At this point, no incompatible modules are known.

Both encoding styles are correct from the YAML standard standpoint, but if your module relies on encodings results bytewise, it may break with this change. Be cautious if you do the following:

• Compare results of YAML encoding as strings.
• Hash results of yaml encoding.