An interesting initiative by Brett Terpstra and The Soulmen: TextBundle is a new file format to bundle Markdown files, metadata, and referenced images in a single file that multiple apps can exchange without asking for additional permissions due to Sandboxing on OS X.
From the website:
The TextBundle file format aims to provide a more seamless user expericence when exchanging Markdown files between sandboxed applications.
Sandboxing is required for all apps available on the Mac and iOS app store, in order to grant users a high level of data security. Sandboxed apps are only permitted access to files explicitly provided by the user - for example Markdown text files. When working with different Markdown applications, sandboxing can cause inconveniences for the user.
Here's Brett's explanation:
The Textbundle format is very simple. A folder containing a plain text file, a JSON data file, and an assets sub-folder. An app, such as Ulysses, can write a Textbundle out and pass it to Marked, and all of the necessary components are automatically included. Images, additional text files, and any metadata needed are all there and safe from sandboxing restrictions.
What's especially intriguing is metadata support: with TextBundle, all kinds of information could be stored in the file and passed across devices and platforms:
This means that data such as revision history, writing statistics, and all kinds of things we haven’t imagined yet can be stored with a file that can move across folders, entire machines, and even platforms.
For new formats to work, they need to be ubiquitous; for Markdown formats to work, they need to be supported by the community of developers who make text editors. Right now, Ulysses III and Marked 2 have added support for TextBundle; developers can check out the official spec here.