Extend .quartoignore to quarto render/preview as a way to exclude files without project.render

[mcanouil]

Make quarto render and quarto preview honour .quartoignore when discovering project input files, so files can be excluded from rendering without maintaining an explicit project.render allowlist in _quarto.yml.

Problem

Today, to keep a .qmd/.ipynb file in the project but out of the render set, the options are:

• Prefix the path with _ or . (changes the filename/URL and affects more than rendering).
• Add it to .gitignore (couples "not rendered" to "not version-controlled", which is often wrong, e.g. drafts I do want in git).
• Switch to an explicit project.render allowlist in _quarto.yml.

The project.render allowlist is the only clean option, but it inverts the model: instead of saying "skip these few files" I must enumerate (and keep enumerating) everything I do want rendered. For large or fast-growing projects this is brittle and easy to forget when adding new files.

Proposal

Treat .quartoignore (already present and documented for quarto use template) as a denylist for project input discovery in quarto render and quarto preview:

• Patterns in .quartoignore exclude matching files from the project render set.
• Reuse the existing gitignore-style syntax, including # comments and ! negation, already parsed for templates.
• A file matched by .quartoignore is skipped by both render and preview (so preview does not watch/re-render it either).

This keeps "what to render" decoupled from "what to commit", needs no _quarto.yml change, and matches the mental model users already have from .gitignore.

Example

my-project/
├── _quarto.yml
├── index.qmd
├── notes/scratch.qmd      # want in git, do not want rendered
└── posts/post-1.qmd

.quartoignore:

notes/

quarto render and quarto preview would render index.qmd and posts/post-1.qmd, skipping notes/scratch.qmd, with no project.render entry and no .gitignore change.

Why this matters

• Lower-friction, denylist-style exclusion that scales as files are added.
• Decouples render exclusion from version control and from filename conventions (_/.).
• Builds on an existing file (.quartoignore) and existing parsing, rather than introducing new config surface.

Open questions

• Precedence relative to project.render, .gitignore, and engine ignore dirs.
• Whether per-directory .quartoignore files nest, or only the project root is read.
• Whether this changes the meaning of .quartoignore for users who rely on its current template-only behaviour.