Add option to only aggregate documentation from selected package versions

README.md

@@ -75,6 +75,34 @@ MultiDocumenter.make(
 )
 ```
 
+### Limiting copied versions and linking to all upstream versions
+
+When aggregating many packages, you can copy only selected deployed versions to reduce storage size of the final website:
+
+```julia
+MultiDocumenter.MultiDocRef(
+    upstream = joinpath(clonedir, "SomePackage"),
+    path = "SomePackage",
+    name = "SomePackage.jl",
+    giturl = "https://github.com/SomeOrg/SomePackage.jl.git",
+    versions = MultiDocumenter.VersionSelection(
+        ["stable", "dev"];
+        # optional: adds a "See All Versions" entry to the version selector
+        all_versions_url = "https://someorg.github.io/SomePackage.jl/",
+    ),
+)
+```
+
+- Only the listed version directories are copied (plus root files like `index.html` and `versions.js`).
+  Versions that do not exist upstream are reported and skipped; if none of them exist, all versions are copied.
+- The package's `index.html` is regenerated to redirect to the **first** version that was copied, and that
+  version becomes the canonical one for the package, so list them in the order you want.
+- `versions.js` is rewritten to include only copied versions, and Documenter's "outdated version" markers
+  (`DOCUMENTER_NEWEST`, `DOCUMENTER_STABLE`) are repointed at versions that were copied.
+- If `all_versions_url` is set, the version selector gets a `See All Versions` entry pointing there, so that
+  the versions that were not copied stay reachable on the upstream site. It must be an absolute `http(s)` URL
+  naming the site root, and is not derived from `giturl`.
+
 ![example](sample.png)
 
 ## Deployment