sapper export --no-subfolders

[bfanger]

The problem
I want src/routes/foo.svelte to match /foo in the url.

Current situation
src/routes/foo.svelte exports to foo/index.html
Certain static hosting providers (github-pages in my case) will see the generated foo folder and will redirect to /foo/ (with a trailing slash) before displaying the contents of the index.html.

This PR
This PR add a --no-subfolders option to sapper export

The option wil generate /export/foo.html from src/routes/foo.svelte
Github pages and others will match the /foo url to the foo.html file without redirect.

The feature behaves similar to the subFolders option in nuxt

The patch itself is very small, couple of lines in cli.ts and export.ts
But i've also included tests (based on the regular export test) and added a line to the documentation.

[bfanger]

I've rebased the upstream changes (fixed the merge conflict)

[benmccann]

Thanks @bfanger. I think folks are a bit nervous about adding more configuration options until we figure out how exactly to handle configuration. I created an RFC to try to move that conversation along, so please feel free to take a look in case you have any comments about it

[bfanger]

After the sapper 0.28+ rebase, the CI failed on (14, macOS-latest) which is weird, because thats the platform i develop and test on, looking at the error i looks like the tests would pass if the CI server was little faster.

And although the test itself is fast, the before('build app') and before('export app') steps are slow. The tests/apps/export takes about 3s to 7s on my beefy machine. That's too close the the 10s limit imposed by the this.timeout(10000);

[benmccann]

The tests seem a bit flaky on Mac. I wouldn't worry about it failing on this PR. We're totally open to improvements to make it more robust though 🙂

[benmccann]

Thanks for putting together this PR! Sapper never had a good method of handling configuration, which made it difficult to know how to integrate this feature. However, that's been addressed in SvelteKit by adding a svelte.config.cjs file and adapters. I'm going to go ahead and close this PR since we won't be adding the feature to Sapper. You might like to check out SvelteKit instead. We'll be reviewing PRs for missing features there

[bfanger]

👍 i'll be switching to SvelteKit. Hope this feature wil be part of it.