Request: Support checking if TOCs are up to date

[adamtheturtle]

I would like to use the tool on CI to confirm that my TOCs are up to date.
One way I can think of to do this is to have a different exit code if the TOCs are not up to date.
Another is to include a --dry-run option and look for output.

[thlorenz]

I like the idea.
It could work the following way:

• generate a toc for the current file (save it in a string)
• pull out the existing toc from the current file and save in another string
• then compare both strings via a diff module and show the updates needed

PRs with tests welcome :)

[kamadorueda]

@adamtheturtle @thlorenz

If you want to run doctoc in the CI, ensuring tocs are up-to-date or fail the job if not, I highly suggest you this:

https://github.com/fluidattacks/makes#formatmarkdown

This is how a CI failure looks like:

fluidattacks/makes#190 (comment)

It can also be executed locally, which is nice

[AndrewSouthpaw]

Closing in favor of #188, keep the conversation going there. 😄