diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index aae5b93e0..fc6531ea5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -88,7 +88,7 @@ jobs:
         fetch-depth: 0
     - uses: cachix/install-nix-action@v17
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
-    - run: echo NIX_VERSION="$(nix-instantiate --eval -E '(import ./default.nix).defaultPackage.${builtins.currentSystem}.version' | tr -d \")" >> $GITHUB_ENV
+    - run: echo NIX_VERSION="$(nix --experimental-features 'nix-command flakes' eval .\#default.version | tr -d \")" >> $GITHUB_ENV
     - uses: cachix/cachix-action@v10
       if: needs.check_cachix.outputs.secret == 'true'
       with:
diff --git a/doc/manual/src/command-ref/nix-build.md b/doc/manual/src/command-ref/nix-build.md
index aacb32a25..49c6f3f55 100644
--- a/doc/manual/src/command-ref/nix-build.md
+++ b/doc/manual/src/command-ref/nix-build.md
@@ -12,6 +12,12 @@
   [`--dry-run`]
   [{`--out-link` | `-o`} *outlink*]
 
+# Disambiguation
+
+This man page describes the command `nix-build`, which is distinct from `nix
+build`. For documentation on the latter, run `nix build --help` or see `man
+nix3-build`.
+
 # Description
 
 The `nix-build` command builds the derivations described by the Nix
diff --git a/doc/manual/src/command-ref/nix-shell.md b/doc/manual/src/command-ref/nix-shell.md
index a2b6d8a8e..840bccd25 100644
--- a/doc/manual/src/command-ref/nix-shell.md
+++ b/doc/manual/src/command-ref/nix-shell.md
@@ -15,6 +15,12 @@
   [`--keep` *name*]
   {{`--packages` | `-p`} {*packages* | *expressions*} … | [*path*]}
 
+# Disambiguation
+
+This man page describes the command `nix-shell`, which is distinct from `nix
+shell`. For documentation on the latter, run `nix shell --help` or see `man
+nix3-shell`.
+
 # Description
 
 The command `nix-shell` will build the dependencies of the specified
diff --git a/flake.lock b/flake.lock
index 31c1910df..01e4f506a 100644
--- a/flake.lock
+++ b/flake.lock
@@ -18,16 +18,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1645296114,
-        "narHash": "sha256-y53N7TyIkXsjMpOG7RhvqJFGDacLs9HlyHeSTBioqYU=",
+        "lastModified": 1653988320,
+        "narHash": "sha256-ZaqFFsSDipZ6KVqriwM34T739+KLYJvNmCWzErjAg7c=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "530a53dcbc9437363471167a5e4762c5fcfa34a1",
+        "rev": "2fa57ed190fd6c7c746319444f34b5917666e5c1",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "nixos-21.05-small",
+        "ref": "nixos-22.05-small",
         "repo": "nixpkgs",
         "type": "github"
       }
diff --git a/flake.nix b/flake.nix
index a69969cfa..d683570af 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,7 +1,7 @@
 {
   description = "The purely functional package manager";
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-21.05-small";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.05-small";
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
 
@@ -36,7 +36,7 @@
           )
       );
 
-      forAllStdenvs = stdenvs: f: nixpkgs.lib.genAttrs stdenvs (stdenv: f stdenv);
+      forAllStdenvs = f: nixpkgs.lib.genAttrs stdenvs (stdenv: f stdenv);
 
       # Memoize nixpkgs for different platforms for efficiency.
       nixpkgsFor =
@@ -88,7 +88,6 @@
             "LDFLAGS=-fuse-ld=gold"
           ];
 
-
         nativeBuildDeps =
           [
             buildPackages.bison
@@ -314,6 +313,7 @@
                   for LIB in $out/lib/*.dylib; do
                     chmod u+w $LIB
                     install_name_tool -id $LIB $LIB
+                    install_name_tool -delete_rpath ${boost}/lib/ $LIB || true
                   done
                   install_name_tool -change ${boost}/lib/libboost_system.dylib $out/lib/libboost_system.dylib $out/lib/libboost_thread.dylib
                 ''}
@@ -370,10 +370,10 @@
                 ++ lib.optional (currentStdenv.isLinux || currentStdenv.isDarwin) libsodium
                 ++ lib.optional currentStdenv.isDarwin darwin.apple_sdk.frameworks.Security;
 
-              configureFlags = ''
-                --with-dbi=${perlPackages.DBI}/${pkgs.perl.libPrefix}
-                --with-dbd-sqlite=${perlPackages.DBDSQLite}/${pkgs.perl.libPrefix}
-              '';
+              configureFlags = [
+                "--with-dbi=${perlPackages.DBI}/${pkgs.perl.libPrefix}"
+                "--with-dbd-sqlite=${perlPackages.DBDSQLite}/${pkgs.perl.libPrefix}"
+              ];
 
               enableParallelBuilding = true;
 
@@ -405,7 +405,7 @@
 
       # A Nixpkgs overlay that overrides the 'nix' and
       # 'nix.perl-bindings' packages.
-      overlay = overlayFor (p: p.stdenv);
+      overlays.default = overlayFor (p: p.stdenv);
 
       hydraJobs = {
 
@@ -430,7 +430,7 @@
           value = let
             nixpkgsCross = import nixpkgs {
               inherit system crossSystem;
-              overlays = [ self.overlay ];
+              overlays = [ self.overlays.default ];
             };
           in binaryTarball nixpkgsFor.${system} self.packages.${system}."nix-${crossSystem}" nixpkgsCross;
         }) crossSystems));
@@ -476,31 +476,31 @@
         tests.remoteBuilds = import ./tests/remote-builds.nix {
           system = "x86_64-linux";
           inherit nixpkgs;
-          inherit (self) overlay;
+          overlay = self.overlays.default;
         };
 
         tests.nix-copy-closure = import ./tests/nix-copy-closure.nix {
           system = "x86_64-linux";
           inherit nixpkgs;
-          inherit (self) overlay;
+          overlay = self.overlays.default;
         };
 
         tests.nssPreload = (import ./tests/nss-preload.nix rec {
           system = "x86_64-linux";
           inherit nixpkgs;
-          inherit (self) overlay;
+          overlay = self.overlays.default;
         });
 
         tests.githubFlakes = (import ./tests/github-flakes.nix rec {
           system = "x86_64-linux";
           inherit nixpkgs;
-          inherit (self) overlay;
+          overlay = self.overlays.default;
         });
 
         tests.sourcehutFlakes = (import ./tests/sourcehut-flakes.nix rec {
           system = "x86_64-linux";
           inherit nixpkgs;
-          inherit (self) overlay;
+          overlay = self.overlays.default;
         });
 
         tests.setuid = nixpkgs.lib.genAttrs
@@ -508,7 +508,7 @@
           (system:
             import ./tests/setuid.nix rec {
               inherit nixpkgs system;
-              inherit (self) overlay;
+              overlay = self.overlays.default;
             });
 
         # Make sure that nix-env still produces the exact same result
@@ -553,8 +553,9 @@
         dockerImage = self.hydraJobs.dockerImage.${system};
       });
 
-      packages = forAllSystems (system: {
+      packages = forAllSystems (system: rec {
         inherit (nixpkgsFor.${system}) nix;
+        default = nix;
       } // (nixpkgs.lib.optionalAttrs (builtins.elem system linux64BitSystems) {
         nix-static = let
           nixpkgs = nixpkgsFor.${system}.pkgsStatic;
@@ -610,12 +611,14 @@
               ln -s ${image} $image
               echo "file binary-dist $image" >> $out/nix-support/hydra-build-products
             '';
-      } // builtins.listToAttrs (map (crossSystem: {
+      }
+
+      // builtins.listToAttrs (map (crossSystem: {
         name = "nix-${crossSystem}";
         value = let
           nixpkgsCross = import nixpkgs {
             inherit system crossSystem;
-            overlays = [ self.overlay ];
+            overlays = [ self.overlays.default ];
           };
         in with commonDeps nixpkgsCross; nixpkgsCross.stdenv.mkDerivation {
           name = "nix-${version}";
@@ -649,44 +652,45 @@
           doInstallCheck = true;
           installCheckFlags = "sysconfdir=$(out)/etc";
         };
-      }) crossSystems)) // (builtins.listToAttrs (map (stdenvName:
+      }) (if system == "x86_64-linux" then crossSystems else [])))
+
+      // (builtins.listToAttrs (map (stdenvName:
         nixpkgsFor.${system}.lib.nameValuePair
           "nix-${stdenvName}"
           nixpkgsFor.${system}."${stdenvName}Packages".nix
       ) stdenvs)));
 
-      defaultPackage = forAllSystems (system: self.packages.${system}.nix);
+      devShells = forAllSystems (system:
+        forAllStdenvs (stdenv:
+          with nixpkgsFor.${system};
+          with commonDeps pkgs;
+          nixpkgsFor.${system}.${stdenv}.mkDerivation {
+            name = "nix";
 
-      devShell = forAllSystems (system: self.devShells.${system}.stdenvPackages);
+            outputs = [ "out" "dev" "doc" ];
 
-      devShells = forAllSystemsAndStdenvs (system: stdenv:
-        with nixpkgsFor.${system};
-        with commonDeps pkgs;
+            nativeBuildInputs = nativeBuildDeps;
+            buildInputs = buildDeps ++ propagatedDeps ++ awsDeps;
 
-        nixpkgsFor.${system}.${stdenv}.mkDerivation {
-          name = "nix";
+            inherit configureFlags;
 
-          outputs = [ "out" "dev" "doc" ];
+            enableParallelBuilding = true;
 
-          nativeBuildInputs = nativeBuildDeps;
-          buildInputs = buildDeps ++ propagatedDeps ++ awsDeps;
+            installFlags = "sysconfdir=$(out)/etc";
 
-          inherit configureFlags;
+            shellHook =
+              ''
+                PATH=$prefix/bin:$PATH
+                unset PYTHONPATH
+                export MANPATH=$out/share/man:$MANPATH
 
-          enableParallelBuilding = true;
-
-          installFlags = "sysconfdir=$(out)/etc";
-
-          shellHook =
-            ''
-              PATH=$prefix/bin:$PATH
-              unset PYTHONPATH
-              export MANPATH=$out/share/man:$MANPATH
-
-              # Make bash completion work.
-              XDG_DATA_DIRS+=:$out/share
-            '';
-        });
+                # Make bash completion work.
+                XDG_DATA_DIRS+=:$out/share
+              '';
+          }
+        )
+        // { default = self.devShells.${system}.stdenv; }
+      );
 
   };
 }
diff --git a/scripts/create-darwin-volume.sh b/scripts/create-darwin-volume.sh
index aee7ff4bf..103e1e391 100755
--- a/scripts/create-darwin-volume.sh
+++ b/scripts/create-darwin-volume.sh
@@ -442,8 +442,9 @@ add_nix_vol_fstab_line() {
     local escaped_mountpoint="${NIX_ROOT/ /'\\\'040}"
     shift
 
-    # wrap `ex` to work around a problem with vim plugins breaking exit codes
-    # (see github.com/NixOS/nix/issues/5468)
+    # wrap `ex` to work around problems w/ vim features breaking exit codes
+    # - plugins (see github.com/NixOS/nix/issues/5468): -u NONE
+    # - swap file: -n
     #
     # the first draft used `--noplugin`, but github.com/NixOS/nix/issues/6462
     # suggests we need the less-semantic `-u NONE`
@@ -456,7 +457,7 @@ add_nix_vol_fstab_line() {
     # minver 10.12.6 seems to have released with vim 7.4
     cat > "$SCRATCH/ex_cleanroom_wrapper" <<EOF
 #!/bin/sh
-/usr/bin/ex -u NONE "\$@"
+/usr/bin/ex -u NONE -n "\$@"
 EOF
     chmod 755 "$SCRATCH/ex_cleanroom_wrapper"
 
@@ -650,9 +651,9 @@ EOF
         task "Configuring /etc/synthetic.conf to make a mount-point at $NIX_ROOT" >&2
         # technically /etc/synthetic.d/nix is supported in Big Sur+
         # but handling both takes even more code...
-        # Note: `-u NONE` disables vim plugins/rc; see note on --clean earlier
+        # See earlier note; `-u NONE` disables vim plugins/rc, `-n` skips swapfile
         _sudo "to add Nix to /etc/synthetic.conf" \
-            /usr/bin/ex -u NONE /etc/synthetic.conf <<EOF
+            /usr/bin/ex -u NONE -n /etc/synthetic.conf <<EOF
 :a
 ${NIX_ROOT:1}
 .
@@ -820,8 +821,8 @@ setup_volume_daemon() {
     local volume_uuid="$2"
     if ! test_voldaemon; then
         task "Configuring LaunchDaemon to mount '$NIX_VOLUME_LABEL'" >&2
-        # Note: `-u NONE` disables vim plugins/rc; see note on --clean earlier
-        _sudo "to install the Nix volume mounter" /usr/bin/ex -u NONE "$NIX_VOLUME_MOUNTD_DEST" <<EOF
+        # See earlier note; `-u NONE` disables vim plugins/rc, `-n` skips swapfile
+        _sudo "to install the Nix volume mounter" /usr/bin/ex -u NONE -n "$NIX_VOLUME_MOUNTD_DEST" <<EOF
 :a
 $(generate_mount_daemon "$cmd_type" "$volume_uuid")
 .
diff --git a/scripts/install-multi-user.sh b/scripts/install-multi-user.sh
index b79a9c23a..9a18280ef 100644
--- a/scripts/install-multi-user.sh
+++ b/scripts/install-multi-user.sh
@@ -638,6 +638,17 @@ place_channel_configuration() {
     fi
 }
 
+check_selinux() {
+    if command -v getenforce > /dev/null 2>&1; then
+        if ! [ "$(getenforce)" = "Disabled" ]; then
+            failure <<EOF
+Nix does not work with selinux enabled yet!
+see https://github.com/NixOS/nix/issues/2374
+EOF
+        fi
+    fi
+}
+
 welcome_to_nix() {
     ok "Welcome to the Multi-User Nix Installation"
 
@@ -866,6 +877,8 @@ when I need to.
 EOF
     fi
 
+    check_selinux
+
     if [ "$(uname -s)" = "Darwin" ]; then
         # shellcheck source=./install-darwin-multi-user.sh
         . "$EXTRACTED_NIX_PATH/install-darwin-multi-user.sh"
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index ddbb401f0..e31336b9e 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -146,7 +146,8 @@ SourceExprCommand::SourceExprCommand(bool supportReadOnlyMode)
         .shortName = 'f',
         .description =
             "Interpret installables as attribute paths relative to the Nix expression stored in *file*. "
-            "If *file* is the character -, then a Nix expression will be read from standard input.",
+            "If *file* is the character -, then a Nix expression will be read from standard input. "
+            "Implies `--impure`.",
         .category = installablesCategory,
         .labels = {"file"},
         .handler = {&file},
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index e173610de..28b05fc2c 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -1066,6 +1066,11 @@ struct CmdRepl : InstallablesCommand
         return file.has_value() or expr.has_value();
     }
 
+    bool forceImpureByDefault() override
+    {
+        return true;
+    }
+
     std::string description() override
     {
         return "start an interactive environment for evaluating Nix expressions";
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 7b8732169..4eaa3c9b0 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -150,7 +150,7 @@ public:
         if (debugRepl)
             runDebugRepl(&error, env, expr);
 
-        throw error;
+        throw std::move(error);
     }
 
     template<class E>
@@ -165,7 +165,7 @@ public:
             runDebugRepl(&e, last.env, last.expr);
         }
 
-        throw e;
+        throw std::move(e);
     }
 
 
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index 35c841897..920726b73 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -513,6 +513,15 @@ LockedFlake lockFlake(
                         if (!lockFlags.allowMutable && !input.ref->input.isLocked())
                             throw Error("cannot update flake input '%s' in pure mode", inputPathS);
 
+                        /* Note: in case of an --override-input, we use
+                            the *original* ref (input2.ref) for the
+                            "original" field, rather than the
+                            override. This ensures that the override isn't
+                            nuked the next time we update the lock
+                            file. That is, overrides are sticky unless you
+                            use --no-write-lock-file. */
+                        auto ref = input2.ref ? *input2.ref : *input.ref;
+
                         if (input.isFlake) {
                             Path localPath = parentPath;
                             FlakeRef localRef = *input.ref;
@@ -524,15 +533,7 @@ LockedFlake lockFlake(
 
                             auto inputFlake = getFlake(state, localRef, useRegistries, flakeCache, inputPath);
 
-                            /* Note: in case of an --override-input, we use
-                               the *original* ref (input2.ref) for the
-                               "original" field, rather than the
-                               override. This ensures that the override isn't
-                               nuked the next time we update the lock
-                               file. That is, overrides are sticky unless you
-                               use --no-write-lock-file. */
-                            auto childNode = std::make_shared<LockedNode>(
-                                inputFlake.lockedRef, input2.ref ? *input2.ref : *input.ref);
+                            auto childNode = std::make_shared<LockedNode>(inputFlake.lockedRef, ref);
 
                             node->inputs.insert_or_assign(id, childNode);
 
@@ -560,7 +561,7 @@ LockedFlake lockFlake(
                             auto [sourceInfo, resolvedRef, lockedRef] = fetchOrSubstituteTree(
                                 state, *input.ref, useRegistries, flakeCache);
                             node->inputs.insert_or_assign(id,
-                                std::make_shared<LockedNode>(lockedRef, *input.ref, false));
+                                std::make_shared<LockedNode>(lockedRef, ref, false));
                         }
                     }
 
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 8813c61a9..5eb022770 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -150,16 +150,16 @@ struct Expr
 };
 
 #define COMMON_METHODS \
-    void show(const SymbolTable & symbols, std::ostream & str) const;    \
-    void eval(EvalState & state, Env & env, Value & v); \
-    void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env);
+    void show(const SymbolTable & symbols, std::ostream & str) const override; \
+    void eval(EvalState & state, Env & env, Value & v) override; \
+    void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env) override;
 
 struct ExprInt : Expr
 {
     NixInt n;
     Value v;
     ExprInt(NixInt n) : n(n) { v.mkInt(n); };
-    Value * maybeThunk(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env) override;
     COMMON_METHODS
 };
 
@@ -168,7 +168,7 @@ struct ExprFloat : Expr
     NixFloat nf;
     Value v;
     ExprFloat(NixFloat nf) : nf(nf) { v.mkFloat(nf); };
-    Value * maybeThunk(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env) override;
     COMMON_METHODS
 };
 
@@ -177,7 +177,7 @@ struct ExprString : Expr
     std::string s;
     Value v;
     ExprString(std::string s) : s(std::move(s)) { v.mkString(this->s.data()); };
-    Value * maybeThunk(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env) override;
     COMMON_METHODS
 };
 
@@ -186,7 +186,7 @@ struct ExprPath : Expr
     std::string s;
     Value v;
     ExprPath(std::string s) : s(std::move(s)) { v.mkPath(this->s.c_str()); };
-    Value * maybeThunk(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env) override;
     COMMON_METHODS
 };
 
@@ -213,7 +213,7 @@ struct ExprVar : Expr
 
     ExprVar(Symbol name) : name(name) { };
     ExprVar(const PosIdx & pos, Symbol name) : pos(pos), name(name) { };
-    Value * maybeThunk(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env) override;
     PosIdx getPos() const override { return pos; }
     COMMON_METHODS
 };
@@ -326,7 +326,7 @@ struct ExprLambda : Expr
         : pos(pos), formals(formals), body(body)
     {
     }
-    void setName(Symbol name);
+    void setName(Symbol name) override;
     std::string showNamePos(const EvalState & state) const;
     inline bool hasFormals() const { return formals != nullptr; }
     PosIdx getPos() const override { return pos; }
@@ -395,15 +395,15 @@ struct ExprOpNot : Expr
         Expr * e1, * e2; \
         name(Expr * e1, Expr * e2) : e1(e1), e2(e2) { }; \
         name(const PosIdx & pos, Expr * e1, Expr * e2) : pos(pos), e1(e1), e2(e2) { }; \
-        void show(const SymbolTable & symbols, std::ostream & str) const \
+        void show(const SymbolTable & symbols, std::ostream & str) const override \
         { \
             str << "("; e1->show(symbols, str); str << " " s " "; e2->show(symbols, str); str << ")"; \
         } \
-        void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)    \
+        void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env) override \
         { \
             e1->bindVars(es, env); e2->bindVars(es, env);    \
         } \
-        void eval(EvalState & state, Env & env, Value & v); \
+        void eval(EvalState & state, Env & env, Value & v) override; \
         PosIdx getPos() const override { return pos; } \
     };
 
diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index 9cbd39247..35fdf807a 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -85,8 +85,9 @@ std::optional<std::string> readHead(const Path & path)
 bool storeCachedHead(const std::string& actualUrl, const std::string& headRef)
 {
     Path cacheDir = getCachePath(actualUrl);
+    auto gitDir = ".";
     try {
-        runProgram("git", true, { "-C", cacheDir, "symbolic-ref", "--", "HEAD", headRef });
+        runProgram("git", true, { "-C", cacheDir, "--git-dir", gitDir, "symbolic-ref", "--", "HEAD", headRef });
     } catch (ExecError &e) {
         if (!WIFEXITED(e.status)) throw;
         return false;
@@ -182,7 +183,7 @@ WorkdirInfo getWorkdirInfo(const Input & input, const Path & workdir)
         if (hasHead) {
             // Using git diff is preferrable over lower-level operations here,
             // because its conceptually simpler and we only need the exit code anyways.
-            auto gitDiffOpts = Strings({ "-C", workdir, "diff", "HEAD", "--quiet"});
+            auto gitDiffOpts = Strings({ "-C", workdir, "--git-dir", gitDir, "diff", "HEAD", "--quiet"});
             if (!submodules) {
                 // Changes in submodules should only make the tree dirty
                 // when those submodules will be copied as well.
@@ -203,6 +204,7 @@ WorkdirInfo getWorkdirInfo(const Input & input, const Path & workdir)
 std::pair<StorePath, Input> fetchFromWorkdir(ref<Store> store, Input & input, const Path & workdir, const WorkdirInfo & workdirInfo)
 {
     const bool submodules = maybeGetBoolAttr(input.attrs, "submodules").value_or(false);
+    auto gitDir = ".git";
 
     if (!fetchSettings.allowDirty)
         throw Error("Git tree '%s' is dirty", workdir);
@@ -210,7 +212,7 @@ std::pair<StorePath, Input> fetchFromWorkdir(ref<Store> store, Input & input, co
     if (fetchSettings.warnDirty)
         warn("Git tree '%s' is dirty", workdir);
 
-    auto gitOpts = Strings({ "-C", workdir, "ls-files", "-z" });
+    auto gitOpts = Strings({ "-C", workdir, "--git-dir", gitDir, "ls-files", "-z" });
     if (submodules)
         gitOpts.emplace_back("--recurse-submodules");
 
@@ -240,7 +242,7 @@ std::pair<StorePath, Input> fetchFromWorkdir(ref<Store> store, Input & input, co
     // modified dirty file?
     input.attrs.insert_or_assign(
         "lastModified",
-        workdirInfo.hasHead ? std::stoull(runProgram("git", true, { "-C", actualPath, "log", "-1", "--format=%ct", "--no-show-signature", "HEAD" })) : 0);
+        workdirInfo.hasHead ? std::stoull(runProgram("git", true, { "-C", actualPath, "--git-dir", gitDir, "log", "-1", "--format=%ct", "--no-show-signature", "HEAD" })) : 0);
 
     return {std::move(storePath), input};
 }
diff --git a/src/libfetchers/github.cc b/src/libfetchers/github.cc
index 0631fb6e8..a491d82a6 100644
--- a/src/libfetchers/github.cc
+++ b/src/libfetchers/github.cc
@@ -381,7 +381,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
 
         Headers headers = makeHeadersWithAuthTokens(host);
 
-        std::string ref_uri;
+        std::string refUri;
         if (ref == "HEAD") {
             auto file = store->toRealPath(
                 downloadFile(store, fmt("%s/HEAD", base_url), "source", false, headers).storePath);
@@ -393,10 +393,11 @@ struct SourceHutInputScheme : GitArchiveInputScheme
             if (!remoteLine) {
                 throw BadURL("in '%d', couldn't resolve HEAD ref '%d'", input.to_string(), ref);
             }
-            ref_uri = remoteLine->target;
+            refUri = remoteLine->target;
         } else {
-            ref_uri = fmt("refs/(heads|tags)/%s", ref);
+            refUri = fmt("refs/(heads|tags)/%s", ref);
         }
+        std::regex refRegex(refUri);
 
         auto file = store->toRealPath(
             downloadFile(store, fmt("%s/info/refs", base_url), "source", false, headers).storePath);
@@ -406,7 +407,7 @@ struct SourceHutInputScheme : GitArchiveInputScheme
         std::optional<std::string> id;
         while(!id && getline(is, line)) {
             auto parsedLine = git::parseLsRemoteLine(line);
-            if (parsedLine && parsedLine->reference == ref_uri)
+            if (parsedLine && parsedLine->reference && std::regex_match(*parsedLine->reference, refRegex))
                 id = parsedLine->target;
         }
 
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index f65fb1b2e..d58ed78b1 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -135,6 +135,7 @@ void LocalStore::addTempRoot(const StorePath & path)
                     state->fdRootsSocket.close();
                     goto restart;
                 }
+                throw;
             }
         }
 
@@ -153,6 +154,7 @@ void LocalStore::addTempRoot(const StorePath & path)
                 state->fdRootsSocket.close();
                 goto restart;
             }
+            throw;
         } catch (EndOfFile & e) {
             debug("GC socket disconnected");
             state->fdRootsSocket.close();
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index feb6899cd..0ee27ecb6 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -802,7 +802,7 @@ public:
         )"};
 
     Setting<StringSet> ignoredAcls{
-        this, {"security.selinux", "system.nfs4_acl"}, "ignored-acls",
+        this, {"security.selinux", "system.nfs4_acl", "security.csm"}, "ignored-acls",
         R"(
           A list of ACLs that should be ignored, normally Nix attempts to
           remove all ACLs from files and directories in the Nix store, but
diff --git a/src/libstore/local-binary-cache-store.cc b/src/libstore/local-binary-cache-store.cc
index a3c3e4806..ba4416f6d 100644
--- a/src/libstore/local-binary-cache-store.cc
+++ b/src/libstore/local-binary-cache-store.cc
@@ -69,6 +69,7 @@ protected:
         } catch (SysError & e) {
             if (e.errNo == ENOENT)
                 throw NoSuchBinaryCacheFile("file '%s' does not exist in binary cache", path);
+            throw;
         }
     }
 
diff --git a/src/libstore/lock.cc b/src/libstore/lock.cc
index f1356fdca..fa718f55d 100644
--- a/src/libstore/lock.cc
+++ b/src/libstore/lock.cc
@@ -67,13 +67,26 @@ bool UserLock::findFreeUser() {
 #if __linux__
             /* Get the list of supplementary groups of this build user.  This
                is usually either empty or contains a group such as "kvm".  */
-            supplementaryGIDs.resize(10);
-            int ngroups = supplementaryGIDs.size();
-            int err = getgrouplist(pw->pw_name, pw->pw_gid,
-                supplementaryGIDs.data(), &ngroups);
-            if (err == -1)
-                throw Error("failed to get list of supplementary groups for '%1%'", pw->pw_name);
+            int ngroups = 32; // arbitrary initial guess
+            supplementaryGIDs.resize(ngroups);
 
+            int err = getgrouplist(pw->pw_name, pw->pw_gid, supplementaryGIDs.data(),
+                                 &ngroups);
+
+            // Our initial size of 32 wasn't sufficient, the correct size has
+            // been stored in ngroups, so we try again.
+            if (err == -1) {
+                supplementaryGIDs.resize(ngroups);
+                err = getgrouplist(pw->pw_name, pw->pw_gid, supplementaryGIDs.data(),
+                                   &ngroups);
+            }
+
+            // If it failed once more, then something must be broken.
+            if (err == -1)
+                throw Error("failed to get list of supplementary groups for '%1%'",
+                            pw->pw_name);
+
+            // Finally, trim back the GID list to its real size
             supplementaryGIDs.resize(ngroups);
 #endif
 
diff --git a/src/libstore/schema.sql b/src/libstore/schema.sql
index 09c71a2b8..d65e5335e 100644
--- a/src/libstore/schema.sql
+++ b/src/libstore/schema.sql
@@ -1,7 +1,7 @@
 create table if not exists ValidPaths (
     id               integer primary key autoincrement not null,
     path             text unique not null,
-    hash             text not null,
+    hash             text not null, -- base16 representation
     registrationTime integer not null,
     deriver          text,
     narSize          integer,
diff --git a/src/libutil/args.hh b/src/libutil/args.hh
index fdd036f9a..07c017719 100644
--- a/src/libutil/args.hh
+++ b/src/libutil/args.hh
@@ -25,6 +25,8 @@ public:
     /* Return a short one-line description of the command. */
     virtual std::string description() { return ""; }
 
+    virtual bool forceImpureByDefault() { return false; }
+
     /* Return documentation about this command, in Markdown format. */
     virtual std::string doc() { return ""; }
 
diff --git a/src/libutil/hilite.cc b/src/libutil/hilite.cc
index a5991ca39..e5088230d 100644
--- a/src/libutil/hilite.cc
+++ b/src/libutil/hilite.cc
@@ -8,9 +8,9 @@ std::string hiliteMatches(
     std::string_view prefix,
     std::string_view postfix)
 {
-    // Avoid copy on zero matches
+    // Avoid extra work on zero matches
     if (matches.size() == 0)
-        return (std::string) s;
+        return std::string(s);
 
     std::sort(matches.begin(), matches.end(), [](const auto & a, const auto & b) {
         return a.position() < b.position();
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 09ccfa591..90418b04d 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -700,4 +700,19 @@ template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 std::string showBytes(uint64_t bytes);
 
 
+/* Provide an addition operator between strings and string_views
+   inexplicably omitted from the standard library. */
+inline std::string operator + (const std::string & s1, std::string_view s2)
+{
+    auto s = s1;
+    s.append(s2);
+    return s;
+}
+
+inline std::string operator + (std::string && s, std::string_view s2)
+{
+    s.append(s2);
+    return std::move(s);
+}
+
 }
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 426f23905..519855ea3 100644
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -543,6 +543,8 @@ static void main_nix_build(int argc, char * * argv)
 
         restoreProcessContext();
 
+        logger->stop();
+
         execvp(shell->c_str(), argPtrs.data());
 
         throw SysError("executing shell '%s'", *shell);
@@ -601,6 +603,8 @@ static void main_nix_build(int argc, char * * argv)
             outPaths.push_back(outputPath);
         }
 
+        logger->stop();
+
         for (auto & path : outPaths)
             std::cout << store->printStorePath(path) << '\n';
     }
diff --git a/src/nix-collect-garbage/nix-collect-garbage.cc b/src/nix-collect-garbage/nix-collect-garbage.cc
index af6f1c88c..e413faffe 100644
--- a/src/nix-collect-garbage/nix-collect-garbage.cc
+++ b/src/nix-collect-garbage/nix-collect-garbage.cc
@@ -37,6 +37,7 @@ void removeOldGenerations(std::string dir)
                 link = readLink(path);
             } catch (SysError & e) {
                 if (e.errNo == ENOENT) continue;
+                throw;
             }
             if (link.find("link") != std::string::npos) {
                 printInfo(format("removing old generations of profile %1%") % path);
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index c412bb814..a69d3700d 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -1485,7 +1485,7 @@ static int main_nix_env(int argc, char * * argv)
         if (globals.profile == "")
             globals.profile = getDefaultProfile();
 
-        op(globals, opFlags, opArgs);
+        op(globals, std::move(opFlags), std::move(opArgs));
 
         globals.state->printStats();
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 9163eefd0..b453ea1ca 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -1093,7 +1093,7 @@ static int main_nix_store(int argc, char * * argv)
         if (op != opDump && op != opRestore) /* !!! hack */
             store = openStore();
 
-        op(opFlags, opArgs);
+        op(std::move(opFlags), std::move(opArgs));
 
         return 0;
     }
diff --git a/src/nix/key-generate-secret.md b/src/nix/key-generate-secret.md
index 4938f637c..609b1abcc 100644
--- a/src/nix/key-generate-secret.md
+++ b/src/nix/key-generate-secret.md
@@ -30,7 +30,7 @@ convert-secret-to-public` to get the corresponding public key for
 verifying signed store paths.
 
 The mandatory argument `--key-name` specifies a key name (such as
-`cache.example.org-1). It is used to look up keys on the client when
+`cache.example.org-1`). It is used to look up keys on the client when
 it verifies signatures. It can be anything, but it’s suggested to use
 the host name of your cache (e.g.  `cache.example.org`) with a suffix
 denoting the number of the key (to be incremented every time you need
diff --git a/src/nix/main.cc b/src/nix/main.cc
index dadb54306..f398e3118 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -380,6 +380,9 @@ void mainWrapped(int argc, char * * argv)
         settings.ttlPositiveNarInfoCache = 0;
     }
 
+    if (args.command->second->forceImpureByDefault() && !evalSettings.pureEval.overridden) {
+        evalSettings.pureEval = false;
+    }
     args.command->second->prepare();
     args.command->second->run();
 }
diff --git a/src/nix/search.cc b/src/nix/search.cc
index 87dc1c0de..f1f5f9641 100644
--- a/src/nix/search.cc
+++ b/src/nix/search.cc
@@ -18,16 +18,24 @@ using namespace nix;
 
 std::string wrap(std::string prefix, std::string s)
 {
-    return prefix + s + ANSI_NORMAL;
+    return concatStrings(prefix, s, ANSI_NORMAL);
 }
 
 struct CmdSearch : InstallableCommand, MixJSON
 {
     std::vector<std::string> res;
+    std::vector<std::string> excludeRes;
 
     CmdSearch()
     {
         expectArgs("regex", &res);
+        addFlag(Flag {
+            .longName = "exclude",
+            .shortName = 'e',
+            .description = "Hide packages whose attribute path, name or description contain *regex*.",
+            .labels = {"regex"},
+            .handler = Handler(&excludeRes),
+        });
     }
 
     std::string description() override
@@ -62,11 +70,16 @@ struct CmdSearch : InstallableCommand, MixJSON
             res.push_back("^");
 
         std::vector<std::regex> regexes;
+        std::vector<std::regex> excludeRegexes;
         regexes.reserve(res.size());
+        excludeRegexes.reserve(excludeRes.size());
 
         for (auto & re : res)
             regexes.push_back(std::regex(re, std::regex::extended | std::regex::icase));
 
+        for (auto & re : excludeRes)
+            excludeRegexes.emplace_back(re, std::regex::extended | std::regex::icase);
+
         auto state = getEvalState();
 
         auto jsonOut = json ? std::make_unique<JSONObject>(std::cout) : nullptr;
@@ -106,6 +119,14 @@ struct CmdSearch : InstallableCommand, MixJSON
                     std::vector<std::smatch> nameMatches;
                     bool found = false;
 
+                    for (auto & regex : excludeRegexes) {
+                        if (
+                            std::regex_search(attrPath2, regex)
+                            || std::regex_search(name.name, regex)
+                            || std::regex_search(description, regex))
+                            return;
+                    }
+
                     for (auto & regex : regexes) {
                         found = false;
                         auto addAll = [&found](std::sregex_iterator it, std::vector<std::smatch> & vec) {
@@ -133,15 +154,15 @@ struct CmdSearch : InstallableCommand, MixJSON
                             jsonElem.attr("version", name.version);
                             jsonElem.attr("description", description);
                         } else {
-                            auto name2 = hiliteMatches(name.name, std::move(nameMatches), ANSI_GREEN, "\e[0;2m");
+                            auto name2 = hiliteMatches(name.name, nameMatches, ANSI_GREEN, "\e[0;2m");
                             if (results > 1) logger->cout("");
                             logger->cout(
                                 "* %s%s",
-                                wrap("\e[0;1m", hiliteMatches(attrPath2, std::move(attrPathMatches), ANSI_GREEN, "\e[0;1m")),
+                                wrap("\e[0;1m", hiliteMatches(attrPath2, attrPathMatches, ANSI_GREEN, "\e[0;1m")),
                                 name.version != "" ? " (" + name.version + ")" : "");
                             if (description != "")
                                 logger->cout(
-                                    "  %s", hiliteMatches(description, std::move(descriptionMatches), ANSI_GREEN, ANSI_NORMAL));
+                                    "  %s", hiliteMatches(description, descriptionMatches, ANSI_GREEN, ANSI_NORMAL));
                         }
                     }
                 }
diff --git a/src/nix/search.md b/src/nix/search.md
index d182788a6..5a5b5ae05 100644
--- a/src/nix/search.md
+++ b/src/nix/search.md
@@ -43,12 +43,23 @@ R""(
   # nix search nixpkgs 'firefox|chromium'
   ```
 
-* Search for packages containing `git'`and either `frontend` or `gui`:
+* Search for packages containing `git` and either `frontend` or `gui`:
 
   ```console
   # nix search nixpkgs git 'frontend|gui'
   ```
 
+* Search for packages containing `neovim` but hide ones containing either `gui` or `python`:
+
+  ```console
+  # nix search nixpkgs neovim -e 'python|gui'
+  ```
+  or
+
+  ```console
+  # nix search nixpkgs neovim -e 'python' -e 'gui'
+  ```
+
 # Description
 
 `nix search` searches *installable* (which must be evaluatable, e.g. a
diff --git a/src/nix/upgrade-nix.cc b/src/nix/upgrade-nix.cc
index 17a5a77ee..2d2453395 100644
--- a/src/nix/upgrade-nix.cc
+++ b/src/nix/upgrade-nix.cc
@@ -34,7 +34,7 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
 
     std::string description() override
     {
-        return "upgrade Nix to the latest stable version";
+        return "upgrade Nix to the stable version declared in Nixpkgs";
     }
 
     std::string doc() override
diff --git a/src/nix/upgrade-nix.md b/src/nix/upgrade-nix.md
index 4d27daad9..084c80ba2 100644
--- a/src/nix/upgrade-nix.md
+++ b/src/nix/upgrade-nix.md
@@ -2,7 +2,7 @@ R""(
 
 # Examples
 
-* Upgrade Nix to the latest stable version:
+* Upgrade Nix to the stable version declared in Nixpkgs:
 
   ```console
   # nix upgrade-nix
@@ -16,8 +16,11 @@ R""(
 
 # Description
 
-This command upgrades Nix to the latest version. By default, it
-locates the directory containing the `nix` binary in the `$PATH`
+This command upgrades Nix to the stable version declared in Nixpkgs.
+This stable version is defined in [nix-fallback-paths.nix](https://github.com/NixOS/nixpkgs/raw/master/nixos/modules/installer/tools/nix-fallback-paths.nix)
+and updated manually. It may not always be the latest tagged release.
+
+By default, it locates the directory containing the `nix` binary in the `$PATH`
 environment variable. If that directory is a Nix profile, it will
 upgrade the `nix` package in that profile to the latest stable binary
 release.
diff --git a/tests/fetchTree-file.sh b/tests/fetchTree-file.sh
index 1c0ce39ce..f0c530466 100644
--- a/tests/fetchTree-file.sh
+++ b/tests/fetchTree-file.sh
@@ -58,7 +58,7 @@ EOF
     nix eval --file - <<EOF
     with (builtins.fromJSON (builtins.readFile ./flake.lock));
 
-    # Url inputs whose extension doesn’t match a know archive format should
+    # Url inputs whose extension doesn’t match a known archive format should
     # not be unpacked by default
     assert (nodes.no_ext_default_no_unpack.locked.type == "file");
     assert (nodes.no_ext_default_no_unpack.locked.unpack or false == false);
diff --git a/tests/flakes.sh b/tests/flakes.sh
index 9a1f0ab6a..36bffcf3b 100644
--- a/tests/flakes.sh
+++ b/tests/flakes.sh
@@ -32,7 +32,7 @@ for repo in $flake1Dir $flake2Dir $flake3Dir $flake7Dir $templatesDir $nonFlakeD
     rm -rf $repo $repo.tmp
     mkdir -p $repo
 
-    # Give one repo a non-master initial branch.
+    # Give one repo a non-main initial branch.
     extraArgs=
     if [[ $repo == $flake2Dir ]]; then
       extraArgs="--initial-branch=main"
@@ -173,11 +173,11 @@ nix build -o $TEST_ROOT/result $flake2Dir#bar --no-write-lock-file
 nix build -o $TEST_ROOT/result $flake2Dir#bar --no-update-lock-file 2>&1 | grep 'requires lock file changes'
 nix build -o $TEST_ROOT/result $flake2Dir#bar --commit-lock-file
 [[ -e $flake2Dir/flake.lock ]]
-[[ -z $(git -C $flake2Dir diff master) ]]
+[[ -z $(git -C $flake2Dir diff main || echo failed) ]]
 
 # Rerunning the build should not change the lockfile.
 nix build -o $TEST_ROOT/result $flake2Dir#bar
-[[ -z $(git -C $flake2Dir diff master) ]]
+[[ -z $(git -C $flake2Dir diff main || echo failed) ]]
 
 # Building with a lockfile should not require a fetch of the registry.
 nix build -o $TEST_ROOT/result --flake-registry file:///no-registry.json $flake2Dir#bar --refresh
@@ -186,7 +186,7 @@ nix build -o $TEST_ROOT/result --no-use-registries $flake2Dir#bar --refresh
 
 # Updating the flake should not change the lockfile.
 nix flake lock $flake2Dir
-[[ -z $(git -C $flake2Dir diff master) ]]
+[[ -z $(git -C $flake2Dir diff main || echo failed) ]]
 
 # Now we should be able to build the flake in pure mode.
 nix build -o $TEST_ROOT/result flake2#bar
@@ -221,7 +221,7 @@ nix build -o $TEST_ROOT/result $flake3Dir#"sth sth"
 nix build -o $TEST_ROOT/result $flake3Dir#"sth%20sth"
 
 # Check whether it saved the lockfile
-(! [[ -z $(git -C $flake3Dir diff master) ]])
+[[ -n $(git -C $flake3Dir diff master) ]]
 
 git -C $flake3Dir add flake.lock
 
@@ -321,10 +321,10 @@ nix build -o $TEST_ROOT/result flake4#xyzzy
 
 # Test 'nix flake update' and --override-flake.
 nix flake lock $flake3Dir
-[[ -z $(git -C $flake3Dir diff master) ]]
+[[ -z $(git -C $flake3Dir diff master || echo failed) ]]
 
 nix flake update $flake3Dir --override-flake flake2 nixpkgs
-[[ ! -z $(git -C $flake3Dir diff master) ]]
+[[ ! -z $(git -C $flake3Dir diff master || echo failed) ]]
 
 # Make branch "removeXyzzy" where flake3 doesn't have xyzzy anymore
 git -C $flake3Dir checkout -b removeXyzzy
diff --git a/tests/github-flakes.nix b/tests/github-flakes.nix
index 7ac397d81..ddae6a21c 100644
--- a/tests/github-flakes.nix
+++ b/tests/github-flakes.nix
@@ -103,7 +103,7 @@ makeTest (
         { config, lib, pkgs, nodes, ... }:
         { virtualisation.writableStore = true;
           virtualisation.diskSize = 2048;
-          virtualisation.pathsInNixDB = [ pkgs.hello pkgs.fuse ];
+          virtualisation.additionalPaths = [ pkgs.hello pkgs.fuse ];
           virtualisation.memorySize = 4096;
           nix.binaryCaches = lib.mkForce [ ];
           nix.extraOptions = "experimental-features = nix-command flakes";
diff --git a/tests/nix-copy-closure.nix b/tests/nix-copy-closure.nix
index 1b63a3fca..ba8b2cfc9 100644
--- a/tests/nix-copy-closure.nix
+++ b/tests/nix-copy-closure.nix
@@ -14,7 +14,7 @@ makeTest (let pkgA = pkgs.cowsay; pkgB = pkgs.wget; pkgC = pkgs.hello; pkgD = pk
     { client =
         { config, lib, pkgs, ... }:
         { virtualisation.writableStore = true;
-          virtualisation.pathsInNixDB = [ pkgA pkgD.drvPath ];
+          virtualisation.additionalPaths = [ pkgA pkgD.drvPath ];
           nix.binaryCaches = lib.mkForce [ ];
         };
 
@@ -22,7 +22,7 @@ makeTest (let pkgA = pkgs.cowsay; pkgB = pkgs.wget; pkgC = pkgs.hello; pkgD = pk
         { config, pkgs, ... }:
         { services.openssh.enable = true;
           virtualisation.writableStore = true;
-          virtualisation.pathsInNixDB = [ pkgB pkgC ];
+          virtualisation.additionalPaths = [ pkgB pkgC ];
         };
     };
 
diff --git a/tests/nss-preload.nix b/tests/nss-preload.nix
index 2610d2b30..64b655ba2 100644
--- a/tests/nss-preload.nix
+++ b/tests/nss-preload.nix
@@ -5,6 +5,42 @@ with import (nixpkgs + "/nixos/lib/testing-python.nix") {
   extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
 };
 
+let
+  nix-fetch = pkgs.writeText "fetch.nix" ''
+    derivation {
+        # This derivation is an copy from what is available over at
+        # nix.git:corepkgs/fetchurl.nix
+        builder = "builtin:fetchurl";
+
+        # We're going to fetch data from the http_dns instance created before
+        # we expect the content to be the same as the content available there.
+        # ```
+        # $ nix-hash --type sha256 --to-base32 $(echo "hello world" | sha256sum | cut -d " " -f 1)
+        # 0ix4jahrkll5zg01wandq78jw3ab30q4nscph67rniqg5x7r0j59
+        # ```
+        outputHash = "0ix4jahrkll5zg01wandq78jw3ab30q4nscph67rniqg5x7r0j59";
+        outputHashAlgo = "sha256";
+        outputHashMode = "flat";
+
+        name = "example.com";
+        url = "http://example.com";
+
+        unpack = false;
+        executable = false;
+
+        system = "builtin";
+
+        preferLocalBuild = true;
+
+        impureEnvVars = [
+            "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
+        ];
+
+        urls = [ "http://example.com" ];
+      }
+  '';
+in
+
 makeTest (
 
 rec {
@@ -68,40 +104,6 @@ rec {
     };
   };
 
-  nix-fetch = pkgs.writeText "fetch.nix" ''
-    derivation {
-        # This derivation is an copy from what is available over at
-        # nix.git:corepkgs/fetchurl.nix
-        builder = "builtin:fetchurl";
-
-        # We're going to fetch data from the http_dns instance created before
-        # we expect the content to be the same as the content available there.
-        # ```
-        # $ nix-hash --type sha256 --to-base32 $(echo "hello world" | sha256sum | cut -d " " -f 1)
-        # 0ix4jahrkll5zg01wandq78jw3ab30q4nscph67rniqg5x7r0j59
-        # ```
-        outputHash = "0ix4jahrkll5zg01wandq78jw3ab30q4nscph67rniqg5x7r0j59";
-        outputHashAlgo = "sha256";
-        outputHashMode = "flat";
-
-        name = "example.com";
-        url = "http://example.com";
-
-        unpack = false;
-        executable = false;
-
-        system = "builtin";
-
-        preferLocalBuild = true;
-
-        impureEnvVars = [
-            "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
-        ];
-
-        urls = [ "http://example.com" ];
-      }
-  '';
-
   testScript = { nodes, ... }: ''
     http_dns.wait_for_unit("nginx")
     http_dns.wait_for_open_port(80)
diff --git a/tests/remote-builds.nix b/tests/remote-builds.nix
index b9e7352c0..7b2e6f708 100644
--- a/tests/remote-builds.nix
+++ b/tests/remote-builds.nix
@@ -61,7 +61,7 @@ in
               }
             ];
           virtualisation.writableStore = true;
-          virtualisation.pathsInNixDB = [ config.system.build.extraUtils ];
+          virtualisation.additionalPaths = [ config.system.build.extraUtils ];
           nix.binaryCaches = lib.mkForce [ ];
           programs.ssh.extraConfig = "ConnectTimeout 30";
         };
diff --git a/tests/repl.sh b/tests/repl.sh
index e9e41558a..30921af04 100644
--- a/tests/repl.sh
+++ b/tests/repl.sh
@@ -42,6 +42,11 @@ testRepl () {
     echo "$replOutput"
     echo "$replOutput" | grep -qs "while evaluating the file" \
       || fail "nix repl --show-trace doesn't show the trace"
+
+    nix repl "${nixArgs[@]}" --option pure-eval true 2>&1 <<< "builtins.currentSystem" \
+      | grep "attribute 'currentSystem' missing"
+    nix repl "${nixArgs[@]}" 2>&1 <<< "builtins.currentSystem" \
+      | grep "$(nix-instantiate --eval -E 'builtins.currentSystem')"
 }
 
 # Simple test, try building a drv
diff --git a/tests/search.sh b/tests/search.sh
index 52e12f381..41b706ac6 100644
--- a/tests/search.sh
+++ b/tests/search.sh
@@ -28,11 +28,18 @@ nix search -f search.nix '' |grep -q hello
 
 e=$'\x1b' # grep doesn't support \e, \033 or even \x1b
 # Multiple overlapping regexes
-(( $(nix search -f search.nix '' 'oo' 'foo' 'oo' | grep "$e\[32;1mfoo$e\\[0;1m" | wc -l) == 1 ))
-(( $(nix search -f search.nix '' 'broken b' 'en bar' | grep "$e\[32;1mbroken bar$e\\[0m" | wc -l) == 1 ))
+(( $(nix search -f search.nix '' 'oo' 'foo' 'oo' | grep -c "$e\[32;1mfoo$e\\[0;1m") == 1 ))
+(( $(nix search -f search.nix '' 'broken b' 'en bar' | grep -c "$e\[32;1mbroken bar$e\\[0m") == 1 ))
 
 # Multiple matches
 # Searching for 'o' should yield the 'o' in 'broken bar', the 'oo' in foo and 'o' in hello
-(( $(nix search -f search.nix '' 'o' | grep -Eo "$e\[32;1mo{1,2}$e\[(0|0;1)m" | wc -l) == 3 ))
+(( $(nix search -f search.nix '' 'o' | grep -Eoc "$e\[32;1mo{1,2}$e\[(0|0;1)m") == 3 ))
 # Searching for 'b' should yield the 'b' in bar and the two 'b's in 'broken bar'
+# NOTE: This does not work with `grep -c` because it counts the two 'b's in 'broken bar' as one matched line
 (( $(nix search -f search.nix '' 'b' | grep -Eo "$e\[32;1mb$e\[(0|0;1)m" | wc -l) == 3 ))
+
+## Tests for --exclude
+(( $(nix search -f search.nix -e hello | grep -c hello) == 0 ))
+
+(( $(nix search -f search.nix foo --exclude 'foo|bar' | grep -Ec 'foo|bar') == 0 ))
+(( $(nix search -f search.nix foo -e foo --exclude bar | grep -Ec 'foo|bar') == 0 ))
diff --git a/tests/setuid.nix b/tests/setuid.nix
index 35eb304ed..a83b1fc3a 100644
--- a/tests/setuid.nix
+++ b/tests/setuid.nix
@@ -10,12 +10,12 @@ with import (nixpkgs + "/nixos/lib/testing-python.nix") {
 makeTest {
   name = "setuid";
 
-  machine =
+  nodes.machine =
     { config, lib, pkgs, ... }:
     { virtualisation.writableStore = true;
       nix.binaryCaches = lib.mkForce [ ];
       nix.nixPath = [ "nixpkgs=${lib.cleanSource pkgs.path}" ];
-      virtualisation.pathsInNixDB = [ pkgs.stdenv pkgs.pkgsi686Linux.stdenv ];
+      virtualisation.additionalPaths = [ pkgs.stdenv pkgs.pkgsi686Linux.stdenv ];
     };
 
   testScript = { nodes }: ''
diff --git a/tests/sourcehut-flakes.nix b/tests/sourcehut-flakes.nix
index 6a1930904..daa259dd6 100644
--- a/tests/sourcehut-flakes.nix
+++ b/tests/sourcehut-flakes.nix
@@ -59,7 +59,7 @@ let
       echo 'ref: refs/heads/master' > $out/HEAD
 
       mkdir -p $out/info
-      echo -e '${nixpkgs.rev}\trefs/heads/master' > $out/info/refs
+      echo -e '${nixpkgs.rev}\trefs/heads/master\n${nixpkgs.rev}\trefs/tags/foo-bar' > $out/info/refs
     '';
 
 in
@@ -106,7 +106,7 @@ makeTest (
           {
             virtualisation.writableStore = true;
             virtualisation.diskSize = 2048;
-            virtualisation.pathsInNixDB = [ pkgs.hello pkgs.fuse ];
+            virtualisation.additionalPaths = [ pkgs.hello pkgs.fuse ];
             virtualisation.memorySize = 4096;
             nix.binaryCaches = lib.mkForce [ ];
             nix.extraOptions = ''
@@ -132,6 +132,17 @@ makeTest (
       client.succeed("curl -v https://git.sr.ht/ >&2")
       client.succeed("nix registry list | grep nixpkgs")
 
+      # Test that it resolves HEAD
+      rev = client.succeed("nix flake info sourcehut:~NixOS/nixpkgs --json | jq -r .revision")
+      assert rev.strip() == "${nixpkgs.rev}", "revision mismatch"
+      # Test that it resolves branches
+      rev = client.succeed("nix flake info sourcehut:~NixOS/nixpkgs/master --json | jq -r .revision")
+      assert rev.strip() == "${nixpkgs.rev}", "revision mismatch"
+      # Test that it resolves tags
+      rev = client.succeed("nix flake info sourcehut:~NixOS/nixpkgs/foo-bar --json | jq -r .revision")
+      assert rev.strip() == "${nixpkgs.rev}", "revision mismatch"
+
+      # Registry and pinning test
       rev = client.succeed("nix flake info nixpkgs --json | jq -r .revision")
       assert rev.strip() == "${nixpkgs.rev}", "revision mismatch"