Support mounting within node_modules directory

[FredKSchott]

Changes

• Astro has shown that there are valid use-cases for mounting a directory from a node_modules as source files.
• This changes our node_modules exclude to only kick in when no mounts are defined. This was the original intended use-case that this support was added for.

Testing

• Covered by tests.

Docs

• N/A

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[mxmul]

I could see this accidentally including node_modules in a multirepo setup (e.g. if we mount ./packages/foo, we probably don't want ./packages/foo/node_modules included).

Ideally, I think we'd still ignore node_modules but only the ones nested under the mount directory. Maybe something like this would do the trick:

    const files = (await new fdir()
      .withFullPaths()
      // Note: exclude() only matches directories, and not files. However, the cost
      // of false positives here is minor, so do this as a quick check to possibly
      // skip scanning into entire folder trees.
-     .exclude((_, dirPath) => foundExcludeMatch(dirPath))
+     .exclude((_, dirPath) => foundExcludeMatch(path.relative(mountKey, dirPath)))
      .crawl(mountKey)
      .withPromise()) as string[];

[FredKSchott]

ah right, we're probably getting this protection for free right now.

I really wanted to avoid making a change to every exclude call, but you're right that this is probably the most clear expression of what we're trying to accomplish here. Mount anything, but never travel down into a nested node_modules within a mount (since those are seen as "third-party" to whatever was just mounted).

[FredKSchott]

// if this is mounted:
/Fred/Code/myapp/node_modules/astro/internal": "/internal"

/Fred/Code/myapp/node_modules/astro/internal/node_modules/...
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ should not be picked up by our automatic "node_modules" exclusion.
                                            ^^^^^^^^^^^^^^ anything inside of this directory should be ignored.

// "any node_modules that is explictly mounted should not be ignored. otherwise, ignore it."

[FredKSchott]

@natemoo-re is going to take this PR over while I'm out!

[drwpow]

👍🏻

[drwpow]

LGTM