Change README.md instructions to be slightly more versatile.

Accept other forks also with type="github".

This is enough to be a bit more convenient in a few more
cases once this propagates into new future projects.

README.md

@@ -2,25 +2,13 @@
 
 ## Usage
 
-> [!WARNING]
-> During the Lix private beta period during which Forgejo is private, this
-> requires configuring netrc in Lix for the tarball download to work.
->
-> Your netrc should look something like so:
-> ```
-> machine git.lix.systems login YOUR-USERNAME password SOME-PERSONAL-ACCESS-TOKEN-REPO-READ
-> ```
->
-> We are terribly sorry for the UX for this being very bad
-> ([issue](https://git.lix.systems/lix-project/lix/issues/254)).
-
 To use, add the following to your `flake.nix`:
 
-<!-- FIXME: this can use the standard non-api archive url when we are
-un-privated -->
-
 ```nix
-inputs.flake-compat.url = "https://git.lix.systems/api/v1/repos/lix-project/flake-compat/archive/main.tar.gz";
+inputs.flake-compat = {
+  url = "github:edolstra/flake-compat";
+  flake = false;
+};
 ```
 
 Afterwards, create a `default.nix` file containing the following:
@@ -30,7 +18,8 @@ Afterwards, create a `default.nix` file containing the following:
   (
     let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
     fetchTarball {
-      url = lock.nodes.flake-compat.locked.url;
+      url = with lock.nodes.flake-compat.locked;
+        "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
       sha256 = lock.nodes.flake-compat.locked.narHash;
     }
   )

default.nix

@@ -8,7 +8,11 @@
 { src, system ? builtins.currentSystem or "unknown-system" }:
 
 let
-
+  id = x: x;
+  overrideWrap' = fn: set: set // { overrideInputs = ov: fn (makeFlakeCompat ov); };
+  overrideWrap = overrideWrap' id;
+  makeFlakeCompat = impureOverrides:
+  let
     lockFilePath = src + "/flake.lock";
 
     lockFile = builtins.fromJSON (builtins.readFile lockFilePath);
@@ -63,17 +67,8 @@ let
               );
           shortRev = builtins.substring 0 7 info.rev;
         }
-    else if info.type == "sourcehut" then
-      { inherit (info) rev narHash lastModified;
-        outPath =
-          fetchTarball
-            ({ url = "https://${info.host or "git.sr.ht"}/${info.owner}/${info.repo}/archive/${info.rev}.tar.gz"; }
-             // (if info ? narHash then { sha256 = info.narHash; } else {})
-            );
-        shortRev = builtins.substring 0 7 info.rev;
-      }
       else
-      # FIXME: add Mercurial inputs.
+        # FIXME: add Mercurial, tarball inputs.
         throw "flake input has unsupported input type '${info.type}'";
 
     callFlake4 = flakeSrc: locks:
@@ -104,22 +99,7 @@ let
         then
           let res = builtins.fetchGit src;
           in if res.rev == "0000000000000000000000000000000000000000" then removeAttrs res ["rev" "shortRev"]  else res
-      else {
-        outPath =
-          # Massage `src` into a store path.
-          if builtins.isPath src
-          then
-            if dirOf (toString src) == builtins.storeDir
-              # `builtins.storePath` is not available in pure-eval mode.
-              && builtins ? currentSystem
-            then
-              # If it's already a store path, don't copy it again.
-              builtins.storePath src
-            else
-              "${src}"
-          else
-            src;
-      };
+        else { outPath = src; };
       # NB git worktrees have a file for .git, so we don't check the type of .git
       isGit = builtins.pathExists (src + "/.git");
       isShallow = builtins.pathExists (src + "/.git/shallow");
@@ -128,6 +108,16 @@ let
       { lastModified = 0; lastModifiedDate = formatSecondsSinceEpoch 0; }
         // (if src ? outPath then src else tryFetchGit src);
 
+
+    nameValuePair = name: value:
+      { inherit name value; };
+    mapAttrs' =
+      # A function, given an attribute's name and value, returns a new `nameValuePair`.
+      f:
+      # Attribute set to map over.
+      set:
+      builtins.listToAttrs (map (attr: f attr set.${attr}) (builtins.attrNames set));
+
     # Format number of seconds in the Unix epoch as %Y%m%d%H%M%S.
     formatSecondsSinceEpoch = t:
       let
@@ -153,6 +143,11 @@ let
         pad = s: if builtins.stringLength s < 2 then "0" + s else s;
       in "${toString y'}${pad (toString m)}${pad (toString d)}${pad (toString hours)}${pad (toString minutes)}${pad (toString seconds)}";
 
+    rootOverrides =
+      mapAttrs'
+        (input: lockKey: nameValuePair lockKey (impureOverrides.${input} or null))
+        lockFile.nodes.${lockFile.root}.inputs;
+
     allNodes =
       builtins.mapAttrs
         (key: node:
@@ -160,13 +155,18 @@ let
             sourceInfo =
               if key == lockFile.root
               then rootSrc
-            else fetchTree (node.info or {} // removeAttrs node.locked ["dir"]);
+              else
+                if rootOverrides.${key} != null then
+                  { type = "path";
+                    outPath = rootOverrides.${key};
+                    narHash = throw "narHash unimplemented for impureOverride";
+                  }
+                else
+                fetchTree (node.info or {} // removeAttrs node.locked ["dir"]);
 
             subdir = if key == lockFile.root then "" else node.locked.dir or "";
 
-          outPath = sourceInfo + ((if subdir == "" then "" else "/") + subdir);
-
-          flake = import (outPath + "/flake.nix");
+            flake = import (sourceInfo + (if subdir != "" then "/" else "") + subdir + "/flake.nix");
 
             inputs = builtins.mapAttrs
               (inputName: inputSpec: allNodes.${resolveInput inputSpec})
@@ -193,21 +193,7 @@ let
 
             outputs = flake.outputs (inputs // { self = result; });
 
-          result =
-            outputs
-            # We add the sourceInfo attribute for its metadata, as they are
-            # relevant metadata for the flake. However, the outPath of the
-            # sourceInfo does not necessarily match the outPath of the flake,
-            # as the flake may be in a subdirectory of a source.
-            # This is shadowed in the next //
-            // sourceInfo
-            // {
-              # This shadows the sourceInfo.outPath
-              inherit outPath;
-
-              inherit inputs; inherit outputs; inherit sourceInfo; _type = "flake";
-            };
-
+            result = outputs // sourceInfo // { inherit inputs; inherit outputs; inherit sourceInfo; };
           in
             if node.flake or true then
               assert builtins.isFunction flake.outputs;
@@ -226,15 +212,17 @@ let
       then allNodes.${lockFile.root}
       else throw "lock file '${lockFilePath}' has unsupported version ${toString lockFile.version}";
 
-in
-  rec {
+  in
+    builtins.mapAttrs (key: attr: overrideWrap' (res: res.${key}) attr)
+      (rec {
         defaultNix =
           (builtins.removeAttrs result ["__functor"])
           // (if result ? defaultPackage.${system} then { default = result.defaultPackage.${system}; } else {})
           // (if result ? packages.${system}.default then { default = result.packages.${system}.default; } else {});
-
         shellNix =
           defaultNix
           // (if result ? devShell.${system} then { default = result.devShell.${system}; } else {})
           // (if result ? devShells.${system}.default then { default = result.devShells.${system}.default; } else {});
-  }
+      });
+
+in makeFlakeCompat {}

flake.nix

@@ -1,6 +0,0 @@
-{
-  description = "Allow flakes to be used with Nix < 2.4";
-
-  outputs = { self }: {
-  };
-}