When loading collection entries, ignore non-markdown files

[erquhart]

Currently every file in a folder based collection is expected to be an entry - even having a .keep file will break the app. Instead, the CMS should simply ignore files that are not markdown.

Requirements

• Check the extensions of entries when loading files for a folder based collection
• If the file extension is md, process as usual
• If the file extension is not md, ignore it

Considerations

• Some markdown files may also need to be ignored, as mentioned in #218
• In lieu of formally accepting a list of files to ignore in the config, we could adopt the convention of ignoring markdown files prefixed with an underscore

[tech4him1]

We wouldn't to just ignore all markdown files that start with an underscore, because some CMS's such as Hugo use them (for example content\_index.md).

[erquhart]

@tech4him1 thanks for that - somehow I wasn't considering that you'd want to edit the index file in the CMS 🙄

[josephearl]

So the files view of the collection should only show files matching the extension defined in the collection or .md if none is defined?

What about .markdown files if I have the extension set to .md - is that something we should handle, or leave for now (also affects https://github.com/netlify/netlify-cms/issues/317)?

[erquhart]

@josephearl we can keep the two issues separate, but fixing both in one shot definitely works too.

[josephearl]

@erquhart one option then is we could allow an array of extensions for a collection (as well as a string if just a single value) - with the default changing from 'md' to ['md', 'markdown']. The first extension would be used when creating files, when listing files it match against any extension in the array; how does that sound?

[erquhart]

@josephearl that works!