Added a way to hook into the serve process.

[AdrienDerobert]

Closes #2573
Added a way to hook into the serve process after the build.

mdbook serve -c <post build command>
# or
mdbook serve --post-build <post build command>

Tested on:

• Linux
• Windows
• MacOs

[szabgab]

Thanks for the PR.

I also think we need a way to do this, but I thought it should be part of the configuration in the book.toml as it is more permanent. In which case would you prefer it to be a command-line flag?

In any case it would be better if there was a test that runs in the CI to check this feature.

[AdrienDerobert]

I can add a configuration option for it in book.toml if you prefer. I was thinking on the easiest and quickest way to develop the feature and the cli flag for serve seemed the simplest to go. As for build you could easily run the build and your command/script right after. But if you prefer i can work a bit more on it to make it part of the configuration and add a test to the ci.

Just to make sure if it is in the book.toml it should also run in build.
Am i right ?

[AdrienDerobert]

Another problem with including this in the book toml config is that the command might be different for a windows user and a user of a posix system. Do I introduce a section per platform to define the command ?