Environments: Add support for include URLs (#29026)

* Preliminary support for include URLs in spack.yaml (environment) files

This commit adds support in environments for external configuration files obtained from a URL with a preference for grabbing raw text from GitHub and gitlab for efficient downloads of the relevant files. The URL can also be a link to a directory that contains multiple configuration files.

Remote configuration files are retrieved and cached for the environment. Configuration files with the same name will not be overwritten once cached.

1 files changed, 13 insertions, 6 deletions

diff --git a/lib/spack/docs/environments.rst b/lib/spack/docs/environments.rst
index 036a33b19f..9be2ab4684 100644
--- a/lib/spack/docs/environments.rst
+++ b/lib/spack/docs/environments.rst
@@ -478,14 +478,21 @@ them to the Environment.
    spack:
      include:
      - relative/path/to/config.yaml
+     - https://github.com/path/to/raw/config/compilers.yaml
      - /absolute/path/to/packages.yaml
 
-Environments can include files with either relative or absolute
-paths. Inline configurations take precedence over included
-configurations, so you don't have to change shared configuration files
-to make small changes to an individual Environment. Included configs
-listed earlier will have higher precedence, as the included configs are
-applied in reverse order.
+Environments can include files or URLs. File paths can be relative or
+absolute. URLs include the path to the text for individual files or
+can be the path to a directory containing configuration files.
+
+^^^^^^^^^^^^^^^^^^^^^^^^
+Configuration precedence
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Inline configurations take precedence over included configurations, so
+you don't have to change shared configuration files to make small changes
+to an individual environment. Included configurations listed earlier will
+have higher precedence, as the included configs are applied in reverse order.
 
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