This PR fixes an issue where a `@source` that's pointing to a folder
that is git ignored, is also ignored by the `@source` even if it's
explicitly added.
Internally, we convert `@source` directives from `PublicSourceEntry`s to
`SourceEntry`s where we have dedicated enum branches for `Auto`,
`Pattern`, `Ignored` and `External`.
The `Auto` one accepts a `base` path, and will be used for auto content
detection. However, these paths will make use of all the default auto
content detection rules, which includes git ignore rules.
We also have `External` where we link to something that's "external" to
the current repo. We can probably improve this name, but it's external
in the sense that it won't show up on GitHub for example, aka ignored.
We have some content dirs that we ignore by default, such as the
`node_modules` folder. When you do use `@source` with `node_modules` in
the path, then we will mark it as an `external` resource which does not
look at the `gitignore` related rules and allowing it to be included
this way.
The idea with this is that, even though the folder is ignored by
default, you can still include files from the folder by explicitly using
the `@source` directive.
The issue as seen in #19844 is using `vendor/` instead of
`node_modules/` which is _not_ ignored by default. While we can add
`vendor/` to this same ignored dirs list, it will result in a breaking
change because this folder is often used by the Laravel community to
store some resources in.
This PR fixes this problem by not only looking at the content dirs we
ignore by default, but also looking at the actual git ignore state of
this folder. If it turns out that this is ignored, then we promote the
`Auto` source to an `External` source.
Fixes: #19844Closes: #20057
## Test plan
1. Added integration tests for this situation
2. Ran the fix on the reproduction from #19844. If we run the CLI with
the `DEBUG=*` environment variable, the log file produces these results:
```diff
diff --git a/./tailwindcss-29207.log b/./tailwindcss-30381.log
index bc3017c..921af0e 100644
--- a/./tailwindcss-29207.log
+++ b/./tailwindcss-30381.log
@@ -6,8 +6,9 @@ INFO tailwindcss_oxide::scanner: Source: PublicSourceEntry { base: "/Users/robin
INFO tailwindcss_oxide::scanner: Optimized sources:
INFO tailwindcss_oxide::scanner: Source: Pattern { base: "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/app/design/frontend/theme", pattern: "/**/*.phtml" }
INFO tailwindcss_oxide::scanner: Source: Pattern { base: "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/app/design/frontend/theme", pattern: "/**/*.xml" }
-INFO tailwindcss_oxide::scanner: Source: Auto { base: "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/vendor/acme/theme" }
+INFO tailwindcss_oxide::scanner: Source: External { base: "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/vendor/acme/theme" }
INFO tailwindcss_oxide::scanner: Source: Ignored { base: "/Users/robin/.fnm/node-versions/v26.1.0/installation/bin", pattern: "/node" }
INFO discover_sources: tailwindcss_oxide::scanner: enter
-INFO discover_sources: tailwindcss_oxide::scanner: Reading "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/app/design/frontend/theme/index.phtml"
+INFO tailwindcss_oxide::scanner: Reading "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/app/design/frontend/theme/index.phtml"
+INFO tailwindcss_oxide::scanner: Reading "/Users/robin/github.com/GrimLink/tailwind-gitignore-bug/vendor/acme/theme/module/templates/component.phtml"
INFO discover_sources: tailwindcss_oxide::scanner: exit
```
We're checking some `.gitignore` related files, so let's check on each
OS [ci-all]
1bf4291e85