tut 0.5.1

Using Tut

I wrote Tut because I wanted an easier way to manage the sample code I was writing for Effective Django. I was using git to track my changes to the text, but those changes weren’t the ones I was reflecting in the code: I could use git to tell me what changed in the text between two points in time, but I couldn’t easily tell what changed between chapters. The code, in effect, was a parallel set of changes, and I was interested in understanding them over the course of the text, not (necessarily) over the course of my writing timeline.

Tut is a command-line tool that makes managing the code changes independently of the text changes more straight-forward. It allows you to define a set of “points” in the development of your source and switch back and forth between them. If you make a change to an early point in your code, you can roll that change forward so your future code is consistent. Under the hood Tut uses git, so you can include your code as a sub-module and use the other git tools you’ve come to appreciate.

To start using Tut, run tut init <path>:

$ tut init ./demosrc

If the path (./demosrc) is not an existing git repository, Tut will initialize one and add an initial commit.

Subsequent Tut commands should be run from within the Tut-managed repository.

$ cd demosrc

To start a point from your current position, run tut start:

$ tut start step_one

After you’ve created different points in your repository, you can run tut points to list them:

$ tut points
step_one
step_two

If you realize you’ve made a mistake and want to change the code at an earlier checkpoint, simply run tut edit:

$ tut edit step_one

Tut will check out the step_one branch, and you can make changes and commit them. Once you’re done editing, commit your changes using git. You’ll also want to roll those changes forward, through the subsequent steps.

$ tut next --merge

Running tut next will find the next step and check out that branch. Adding --merge will also merge the previous step. If we’re done making changes to step_one, running tut next --merge will move us to step_two and merge step_one.

Including Code in Sphinx

Sphinx provides the literalinclude directive, which allows you to include source files, or parts of files, in your documentation. Tut allows you to switch to a specific git tag, branch, or commit before processing the inclusion.

To enable Tut, add tut.sphinx to the list of enabled extensions in your Sphinx project’s conf.py file:

extensions = [
    # ...
    'tut.sphinx',
]

The checkpoint directive takes a single argument, which is the git reference to switch to. For example, the following directive will checkout step_one (either a branch or tag) in the git repository in /src:

.. tut:checkpoint:: step_one
   :path: /src

The directive doesn’t result in any output, but literalinclude (or other file-system inclusion directives) that come after the checkpoint will use the newly checked-out version.

Tut records the starting state of repositories the first time it does a checkout, and restores the initial state after the build completes.

If your document contains multiple checkpoints, you can specify the path once using the tut directive:

.. tut::
   :path: /src

Note that /src is evaluated using the same rules as govern literalinclude. That is, the file name is usually relative to the current file’s path. However, if it is absolute (starting with /), it is relative to the top source directory.

Within a checkpoint Tut provides two new directives for fetching content: tut:literalinclude and tut:diff.

tut:literalinclude works a lot like Sphinx’s built-in literalinclude directive. However, instead of loading the file from the filesystem directly, tut:literalinclude retrieves it from the git repository.

For example:

.. tut:checkpoint:: step_two
   :path: /src

   ...

.. tut:literalinclude:: setup.py

Will fetch setup.py from the step_two branch in the git repository located at /src.

Tut can also show the changes between two checkpoints (branches) using the tut:diff directive. Like tut:literalinclude it uses the git repository referenced in the last checkpoint by default. You can specify the ref and prev_ref to compare; if omitted, ref defaults to the current checkpoint and prev_ref defaults to the previous point, as listed in the output of tut points.

.. tut:diff:: setup.py
  :ref: step_two
  :prev_ref: step_one
  :path: /src/demosrc

N.B.

When Sphinx encounters a checkpoint directive, it performs a git checkout in target repository. This means that the repository should not contain uncommitted changes, to avoid errors on checkout.

Note that this will probably change soon, to allow for more flexible use of content from the git repository.

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