Add -m arg to watch/serve to only watch .md files

[9999years]

Sometimes, a change to a garbage file (in my case, Vim swap files) in the source directory will cause a book rebuild, which is unnecessary, particularly in serve mode where it triggers a visually noisy page refresh.

This PR adds a -m / --markdown-only switch to the watch and serve subcommands, which causes the file-watcher to ignore changes in files that don't end in .md.

[9999years]

This might close or partially close #383. We could also consider using a user-supplied regex for files to watch.

[Michael-F-Bryan]

Instead of using a command-line flag (which you have to remember every time you run mdbook) that only whitelists markdown files, I imagine people would want a more flexible solution where you can provide your own glob patterns to ignore. It'd be annoying if you were {{#include ...}}-ing a *.rs file in your document (which lots of tutorial-style documents do) and mdbook didn't rebuild when it changes.

For example,

[build]
# provide a list of globs to ignore
ignored = [
  "*.tmp",
  "*~",
]

# or use your gitignore file (e.g. with https://crates.io/crates/ignore)

[build]
ignored = "gitignore"

Also, should this alter just the behaviour of file watcher in mdbook watch and mdbook serve, or could it also be used to prevent things from accidentally being copied to the book/ output directory?

[9999years]

I would be fine with either of those, although I feel like ignoring editor-dependent things like swap files should be an end-user task, not bundled with the repository; I feel the same way about putting .*.swp in a .gitignore; they belong, in my opinion, in a global .gitignore.

I only have a narrow need here: excluding my Vim swap files. Any solution that can accomplish that is fine by me. If you’d like to decide on a more flexible system, I’ll see what I can do to help implement it.

[ehuss]

I'm going to close as this is somewhat outdated. Support for .gitignore has been added, and there is more discussion at #1187 and #1440 to configure what to ignore. Thanks for the PR, though!