Assemble experimental feature docs outside of Nix itself

Instead of constructing a markdown list in C++ (which involved all sorts
of nasty string literals), export some JSON and assemble it with the
manual build system.

Besides following the precedent set with other dumped data, this is a
better separate of content and presentation; if we decide for example we
want to display this information in a different way, or in a different
section of the manual, it will become much easier to do so.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/nix/main.cc b/src/nix/main.cc
index 4d4164333..62b1f98d1 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -374,6 +374,11 @@ void mainWrapped(int argc, char * * argv)
         return;
     }
 
+    if (argc == 2 && std::string(argv[1]) == "__dump-xp-features") {
+        logger->cout(documentExperimentalFeatures().dump());
+        return;
+    }
+
     Finally printCompletions([&]()
     {
         if (completions) {