There are many ways to document your application. You could write a text file to be included among your sources, but that is its very problem: it must be found among many other files so they can be easily overlooked. Besides, it has to be simply formatted unless you want your users to have a specific reader: acrobat, word, etc.
Another way, and the one we're going to cover here, is using a markup language to write a textual file to be used as source by a builder to create a richly formated web based documentation. Here there're many markup options but the two main ones are Markdown and ReStructuredTex (RST): the later is more extensible and the de facto standard in Python world, but the former is simpler, easy to use and the default option in Github.
To host generated web documentation you could use any web server but there are many free services out there for open source projects. Here we are going to cover Github wikis and ReadTheDocs service.
Easiest of all is Github that allows documentation hosting throught its wiki pages. Github wikis allows you to use both markdown and RST, editing page directly on Github through a browser or downloading wiki pages as a git repository, apart from the one of your source code. Just keep in mind that although you can make branches, in your wiki git repository, only
pushes to master branch will be rendered and displayed on Github. URL to clone your wiki repository can be found in Github wiki tab. Besides, be aware that if you push your pages files you are supossed to give page files a standard extension: .md for Markdown or .rst for reStructuredText.
Besides documentation editing can be perfomed collaboratively asigning permissions to different users.
To create a new wiki in your Github repository just click on wiki tab inside your project page and add a new page. You can include images already included in any folder inside your repository, add links, sidebars and even footers.
The page called Home is going to be your default landing page. I haven't found a way to order pages in default toolbar so, to keep a kind of index, I use to include in my home page a table of contents with links to pages. Of course you could create a custom sidebar too with correct order pages but it will be under pages sidebar which I don't know yet how to hide it.
Github wikis are easy to use and possibly powerful enough for most projects, but sometimes you need a nicer formatting or a documentation site not related to your code repository on Github, there is where ReadTheDocs comes into play. ReadTheDocs can be connected throught webhooks to Github repository, so any pushes on that repository is going to fire documentation build process automatically. Besides it can keep multiple versions of your documentation, which is useful if your
application usage differs depending on the version the user is using, and it can build a PDF or ePUB files of your documentation to make it available to be downloaded.
Once you register in ReadTheDocs you should go to Settings --> Connected Services to link ReadTheDocs account to the one you use in Github or Bitbucket. After that you should go to My Projects --> Import a Project to create the connection with the repository where your documentation is. You are going to be asked about which name to put for documentation project. That name is going to be used to assign a public URL to your project.
Nevertheless, be aware that you cannot change your project name later (you only could remove project and recreate later with another name). Why you would want to change your project name? maybe you realize another name better or any of it's character happens to be troublesome, for instance I created a project called "vdist-" (note hyphen), after some time I realized that generated url (http://vdist-.readthedocs.io/en/latest/) didn't rendered at all in some browsers and from some locations (my PC chrome browser got page right but my smartphone chrome gave me a DNS error). I recreated project using "vdistdocs" as project name and problem was solved.
I don't know what happens in Bitbucket, but in Github you must allow webhooks updates to ReadTheDocs through your Settings --> Webhooks Github page.
When your project appears in your project pages you can click on them to enter its settings. There you can set type of markup used in your documentation. Markdown is specifically identified and RST is any of the Sphink-like options. In Advanced Settings you can set to create a PDF or ePUB version of your documentation with each build and you can set if your project should be publicly available. Apart from that, ReadTheDocs has a lot of black magic features to be configured through its settings, but I think the simplest configuration you would need includes the parameters I've explained.
For me, the hardest part to configure ReadTheDocs was to figure out which document file structure was needed to let ReadTheDocs render them right. There are two possible setups depending whether your documentation is Markdown or RST based.
For Markdown documentation you should include a mkdocs.yml file in your repository. That file contains the very basic configuration needed by ReadTheDocs to render our documentation. An example of this file could be the one from vdist project:
- [index.md, Home]
- [whatisvdist.md, What is vdist]
- [usecases.md, Use cases]
- [howtoinstall.md, How to install]
- [howtouse.md, How to use]
- [howtocustomize.md, How to customize]
- [buildenvironment.md, Optimizing your build environment]
- [qanda.md, Questions and Answers]
- [howtocontribute.md, How to contribute]
- [releasenotes.md, Release notes]
- [roadmap.md, Development roadmap]
As you can see, mkdocs.yml is simple. It only contains your project name, to be displayed as the title of your documentation site, visual theme to apply to rendered documentation and a table of content linking your markdown pages with each section. That table of contents is the one that will appear as a left sidebar when documentation is rendered.
Using mkdocs file as a guideline, ReadTheDocs will search for a doc o docs folder inside your repository, rendering its contents, if none of those folders is found ReadTheDocs will search in top level forlder of your project.
For RST documentation, process is similar but what it is used as a guideline is a conf.py file generated with Sphinx. Here is a nice tutorial about how to setup sphinx to create files to be imported in ReadTheDocs.
The only problem I've found about ReadTheDocs is not exactly related to them but with their compatibility with RST documentation generated for Github wikis. Problem is that Github wikis expects your RST links to be formatted diferently as ReadTheDocs does. There is a good stackoverflow discussion about the topic. You should aware of it to structure in advance your documentation with the workaround explained there if you want to publish on both Github and ReadTheDocs.