Put functional tests in `tests/functional`

I think it is bad for these reasons when `tests/` contains a mix of
functional and integration tests

 - Concepts is harder to understand, the documentation makes a good
   unit vs functional vs integration distinction, but when the
   integration tests are just two subdirs within `tests/` this is not
   clear.

 - Source filtering in the `flake.nix` is more complex. We need to
   filter out some of the dirs from `tests/`, rather than simply pick
   the dirs we want and take all of them. This is a good sign the
   structure of what we are trying to do is not matching the structure
   of the files.

With this change we have a clean:
```shell-session
$ git show 'HEAD:tests'
tree HEAD:tests

functional/
installer/
nixos/
```

(cherry picked from commit 68c81c737571794f7246db53fb4774e94fcf4b7e)

1 files changed, 187 insertions, 0 deletions

diff --git a/tests/functional/nix-profile.sh b/tests/functional/nix-profile.sh
new file mode 100644
index 000000000..7c478a0cd
--- /dev/null
+++ b/tests/functional/nix-profile.sh
@@ -0,0 +1,187 @@
+source common.sh
+
+clearStore
+clearProfiles
+
+enableFeatures "ca-derivations"
+restartDaemon
+
+# Make a flake.
+flake1Dir=$TEST_ROOT/flake1
+mkdir -p $flake1Dir
+
+cat > $flake1Dir/flake.nix <<EOF
+{
+  description = "Bla bla";
+
+  outputs = { self }: with import ./config.nix; rec {
+    packages.$system.default = mkDerivation {
+      name = "profile-test-\${builtins.readFile ./version}";
+      outputs = [ "out" "man" "dev" ];
+      builder = builtins.toFile "builder.sh"
+        ''
+          mkdir -p \$out/bin
+          cat > \$out/bin/hello <<EOF
+          #! ${shell}
+          echo Hello \${builtins.readFile ./who}
+          EOF
+          chmod +x \$out/bin/hello
+          echo DONE
+          mkdir -p \$man/share/man
+          mkdir -p \$dev/include
+        '';
+      __contentAddressed = import ./ca.nix;
+      outputHashMode = "recursive";
+      outputHashAlgo = "sha256";
+      meta.outputsToInstall = [ "out" "man" ];
+    };
+  };
+}
+EOF
+
+printf World > $flake1Dir/who
+printf 1.0 > $flake1Dir/version
+printf false > $flake1Dir/ca.nix
+
+cp ./config.nix $flake1Dir/
+
+# Test upgrading from nix-env.
+nix-env -f ./user-envs.nix -i foo-1.0
+nix profile list | grep -A2 'Index:.*0' | grep 'Store paths:.*foo-1.0'
+nix profile install $flake1Dir -L
+nix profile list | grep -A4 'Index:.*1' | grep 'Locked flake URL:.*narHash'
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+[ -e $TEST_HOME/.nix-profile/share/man ]
+(! [ -e $TEST_HOME/.nix-profile/include ])
+nix profile history
+nix profile history | grep "packages.$system.default: ∅ -> 1.0"
+nix profile diff-closures | grep 'env-manifest.nix: ε → ∅'
+
+# Test XDG Base Directories support
+
+export NIX_CONFIG="use-xdg-base-directories = true"
+nix profile remove 1
+nix profile install $flake1Dir
+[[ $($TEST_HOME/.local/state/nix/profile/bin/hello) = "Hello World" ]]
+unset NIX_CONFIG
+
+# Test upgrading a package.
+printf NixOS > $flake1Dir/who
+printf 2.0 > $flake1Dir/version
+nix profile upgrade 1
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello NixOS" ]]
+nix profile history | grep "packages.$system.default: 1.0, 1.0-man -> 2.0, 2.0-man"
+
+# Test 'history', 'diff-closures'.
+nix profile diff-closures
+
+# Test rollback.
+nix profile rollback
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+
+# Test uninstall.
+[ -e $TEST_HOME/.nix-profile/bin/foo ]
+nix profile remove 0
+(! [ -e $TEST_HOME/.nix-profile/bin/foo ])
+nix profile history | grep 'foo: 1.0 -> ∅'
+nix profile diff-closures | grep 'Version 3 -> 4'
+
+# Test installing a non-flake package.
+nix profile install --file ./simple.nix ''
+[[ $(cat $TEST_HOME/.nix-profile/hello) = "Hello World!" ]]
+nix profile remove 1
+nix profile install $(nix-build --no-out-link ./simple.nix)
+[[ $(cat $TEST_HOME/.nix-profile/hello) = "Hello World!" ]]
+
+# Test wipe-history.
+nix profile wipe-history
+[[ $(nix profile history | grep Version | wc -l) -eq 1 ]]
+
+# Test upgrade to CA package.
+printf true > $flake1Dir/ca.nix
+printf 3.0 > $flake1Dir/version
+nix profile upgrade 0
+nix profile history | grep "packages.$system.default: 1.0, 1.0-man -> 3.0, 3.0-man"
+
+# Test new install of CA package.
+nix profile remove 0
+printf 4.0 > $flake1Dir/version
+printf Utrecht > $flake1Dir/who
+nix profile install $flake1Dir
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello Utrecht" ]]
+[[ $(nix path-info --json $(realpath $TEST_HOME/.nix-profile/bin/hello) | jq -r .[].ca) =~ fixed:r:sha256: ]]
+
+# Override the outputs.
+nix profile remove 0 1
+nix profile install "$flake1Dir^*"
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello Utrecht" ]]
+[ -e $TEST_HOME/.nix-profile/share/man ]
+[ -e $TEST_HOME/.nix-profile/include ]
+
+printf Nix > $flake1Dir/who
+nix profile upgrade 0
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello Nix" ]]
+[ -e $TEST_HOME/.nix-profile/share/man ]
+[ -e $TEST_HOME/.nix-profile/include ]
+
+nix profile remove 0
+nix profile install "$flake1Dir^man"
+(! [ -e $TEST_HOME/.nix-profile/bin/hello ])
+[ -e $TEST_HOME/.nix-profile/share/man ]
+(! [ -e $TEST_HOME/.nix-profile/include ])
+
+# test priority
+nix profile remove 0
+
+# Make another flake.
+flake2Dir=$TEST_ROOT/flake2
+printf World > $flake1Dir/who
+cp -r $flake1Dir $flake2Dir
+printf World2 > $flake2Dir/who
+
+nix profile install $flake1Dir
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+expect 1 nix profile install $flake2Dir
+diff -u <(
+    nix --offline profile install $flake2Dir 2>&1 1> /dev/null \
+        | grep -vE "^warning: " \
+        | grep -vE "^error \(ignored\): " \
+        || true
+) <(cat << EOF
+error: An existing package already provides the following file:
+
+         $(nix build --no-link --print-out-paths ${flake1Dir}"#default.out")/bin/hello
+
+       This is the conflicting file from the new package:
+
+         $(nix build --no-link --print-out-paths ${flake2Dir}"#default.out")/bin/hello
+
+       To remove the existing package:
+
+         nix profile remove path:${flake1Dir}#packages.${system}.default
+
+       The new package can also be installed next to the existing one by assigning a different priority.
+       The conflicting packages have a priority of 5.
+       To prioritise the new package:
+
+         nix profile install path:${flake2Dir}#packages.${system}.default --priority 4
+
+       To prioritise the existing package:
+
+         nix profile install path:${flake2Dir}#packages.${system}.default --priority 6
+EOF
+)
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+nix profile install $flake2Dir --priority 100
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+nix profile install $flake2Dir --priority 0
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World2" ]]
+# nix profile install $flake1Dir --priority 100
+# [[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+
+# Ensure that conflicts are handled properly even when the installables aren't
+# flake references.
+# Regression test for https://github.com/NixOS/nix/issues/8284
+clearProfiles
+nix profile install $(nix build $flake1Dir --no-link --print-out-paths)
+expect 1 nix profile install --impure --expr "(builtins.getFlake ''$flake2Dir'').packages.$system.default"