feat(nix/sparseTree): add optional name argument

This allows pinning the name of the sparse tree derivation, which
stops the continous rebuilding of tvix-store-proto dependents.

I've opted to let the function take an attribute set instead and
refactored the call sites appropriately.

Change-Id: I3e57785094b1adbfffa24caf9f1c3384844fa200
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8965
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

nix/sparseTree/default.nix

@@ -2,22 +2,33 @@
 # and directories if they are listed in a supplied list:
 #
 # # A very minimal depot
-# sparseTree ./depot [
+# sparseTree {
+#   root = ./depot;
+#   paths = [
 #     ./default.nix
 #     ./depot/nix/readTree/default.nix
 #     ./third_party/nixpkgs
 #     ./third_party/overlays
-# ]
+#   ];
+# }
 { pkgs, lib, ... }:
 
-# root path to use as a reference point
-root:
-# list of paths below `root` that should be
-# included in the resulting directory
-#
-# If path, need to refer to the actual file / directory to be included.
-# If a string, it is treated as a string relative to the root.
-paths:
+{
+  # root path to use as a reference point
+  root
+, # list of paths below `root` that should be
+  # included in the resulting directory
+  #
+  # If path, need to refer to the actual file / directory to be included.
+  # If a string, it is treated as a string relative to the root.
+  paths
+, # (optional) name to use for the derivation
+  #
+  # This should always be set when using roots that do not have
+  # controlled names, such as when passing the top-level of a git
+  # repository (e.g. `depot.path.origSrc`).
+  name ? builtins.baseNameOf root
+}:
 
 let
   rootLength = builtins.stringLength (toString root);
@@ -63,7 +74,7 @@ in
 
 # TODO(sterni): teach readTree to also read symlinked directories,
   # so we ln -sT instead of cp -aT.
-pkgs.runCommand "sparse-${builtins.baseNameOf root}" { } (
+pkgs.runCommand "sparse-${name}" { } (
   lib.concatMapStrings
     ({ src, dst }: ''
       mkdir -p "$(dirname "$out${dst}")"

tvix/store/protos/default.nix

@@ -9,4 +9,8 @@ let
   protoFileNames = filter (hasSuffix ".proto") (attrNames (readDir ./.));
   protoFiles = map (f: ./. + ("/" + f)) protoFileNames;
 in
-depot.nix.sparseTree depot.path.origSrc protoFiles
+depot.nix.sparseTree {
+  name = "tvix-store-protos";
+  root = depot.path.origSrc;
+  paths = protoFiles;
+}

users/grfn/xanthous/server/default.nix

@@ -10,10 +10,13 @@ depot.third_party.naersk.buildPackage {
 
   # Workaround for a potential Nix bug related to restricted eval.
   # See https://github.com/nix-community/naersk/issues/169
-  root = depot.nix.sparseTree ./. [
+  root = depot.nix.sparseTree {
+    root = ./.;
+    paths = [
       ./Cargo.toml
       ./Cargo.lock
     ];
+  };
 
   passthru = {
     docker = import ./docker.nix args;

users/tazjin/tgsa/default.nix

@@ -1,11 +1,14 @@
 { depot, pkgs, ... }:
 
 depot.third_party.naersk.buildPackage {
-  src = depot.nix.sparseTree ./. [
+  src = depot.nix.sparseTree {
+    root = ./.;
+    paths = [
       ./Cargo.lock
       ./Cargo.toml
       ./src
     ];
+  };
 
   buildInputs = with pkgs; [
     pkg-config

web/bubblegum/default.nix

@@ -10,7 +10,11 @@ let
     nint
     ;
 
-  minimalDepot = sparseTree depot.path.origSrc [
+  minimalDepot = sparseTree {
+    root = depot.path.origSrc;
+    name = "minimal-depot";
+
+    paths = [
       # general depot things
       "default.nix"
       "nix/readTree"
@@ -27,6 +31,7 @@ let
       # for blog.nix
       "users/sterni/nix"
     ];
+  };
 
   statusCodes = {
     # 1xx