Add IFD-free gitignoreSource implementation

tests/default.nix

@@ -0,0 +1,24 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  testdata = import ./testdata.nix { inherit pkgs; };
+  runner = import ./runner.nix { inherit pkgs; };
+in
+{
+  plain = runner.makeTest { name = "plain"; rootDir = testdata.sourceUnfiltered + "/test-tree"; };
+  nested = runner.makeTest { name = "nested"; rootDir = testdata.sourceUnfilteredRecursive + "/test-tree"; };
+
+  plain-with-testdata-dir = runner.makeTest { name = "plain"; rootDir = testdata.sourceUnfiltered; };
+  nested-with-testdata-dir = runner.makeTest { name = "nested"; rootDir = testdata.sourceUnfilteredRecursive; };
+  
+  plain-with-testdata-subdir = runner.makeTest { name = "plain"; rootDir = testdata.sourceUnfiltered; subpath = "test-tree"; };
+  nested-with-testdata-subdir = runner.makeTest { name = "nested"; rootDir = testdata.sourceUnfilteredRecursive; subpath = "test-tree"; };
+  
+  subdir-1 = runner.makeTest { name = "subdir-1"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "1-simpl"; };
+  subdir-1x = runner.makeTest { name = "subdir-1x"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "1-xxxxx"; };
+  subdir-2 = runner.makeTest { name = "subdir-2"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "2-negation"; };
+  subdir-3 = runner.makeTest { name = "subdir-3"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "3-wildcards"; };
+  subdir-4 = runner.makeTest { name = "subdir-4"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "4-escapes"; };
+  subdir-9 = runner.makeTest { name = "subdir-9"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "9-expected"; };
+
+}

tests/runner.nix

@@ -0,0 +1,126 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  inherit (pkgs) lib;
+  inherit (import ../. { inherit lib; }) gitignoreFilter gitignoreSource;
+  inherit (lib) concatMap flip;
+  inherit (lib.attrsets) mapAttrsToList nameValuePair;
+  inherit (lib.strings) concatStringsSep;
+  for = l: f: concatMap f l;
+  guard = b: if b then [{}] else [];
+
+  addPath = p: subp: if subp == "" then p else p + "/${subp}";
+
+  /*
+    Make a test case.
+
+      name:                    Name of the test case.
+
+      rootDir:                 Source for the native git implementation.
+                               This is the root of the git repo; as required
+                               by the native git implementation.
+
+      rootDir + "/${subpath}": Source for the Nix implementation, which ought to
+                               discover rootDir by itself.
+
+   */
+  makeTest = {name ? "source", rootDir, subpath ? ""}:
+    pkgs.runCommand "test-${name}" {
+      inherit name;
+      viaGit = listingViaGit { inherit name rootDir subpath; };
+      viaNix = listingViaNixGitignore { inherit name rootDir subpath; };
+    } ''
+      if diff $viaNix $viaGit; then
+        touch $out
+      else
+        echo
+        echo "Found a difference between nix-gitignore and native git."
+        echo "Above diff can be read as a 'fix' to the nix-gitignore output."
+        echo "< fix by excluding this in nix-gitignore"
+        echo "> fix by including this in nix-gitignore"
+        exit 1;
+      fi
+    '';
+
+  listingViaGit = {name ? "source", rootDir, subpath}:
+    pkgs.stdenv.mkDerivation {
+      name = "${name}-listing-via-git";
+      src = rootDir;
+      buildInputs = [pkgs.git];
+      buildPhase = ''
+        if ! test -d .git; then
+          rm .git || true
+          git init mkrepo
+          mv mkrepo/.git . || true
+          rm -rf mkrepo
+        fi
+        git add .
+        git config user.email a@b.c
+        git config user.name abc
+        git commit -m 'Add everything'
+        git archive HEAD -- ${subpath} | tar -t --quoting-style=literal | sed -e 's_/$__' -e 's@^${subpath}/*@@' | (grep -v '^$' || true) | sort >$out
+      '';
+      preInstall = "";
+      installPhase = ":";
+    };
+
+  listingViaNixGitignore = {name ? "source", rootDir, subpath}:
+    pkgs.stdenv.mkDerivation {
+      name = "${name}-listing-via-nix";
+      src = rootDir;
+      buildInputs = [
+        pkgs.git pkgs.nix pkgs.jq
+        # optional 
+        pkgs.git-crypt
+        ];
+      NIX_PATH="nixpkgs=${pkgs.path}";
+      inherit subpath;
+      buildPhase = ''
+        export NIX_LOG_DIR=$TMPDIR
+        export NIX_STATE_DIR=$TMPDIR
+        test -n "$subpath" && cd $subpath
+        nix-instantiate --eval --expr --json \
+            --readonly-mode --option sandbox false \
+            '(import ${gitignoreSource ../.}/tests/runner.nix {}).toStringNixGitignore ./.' \
+          | jq -r . \
+          | sort \
+          >$out
+      '';
+      preInstall = "";
+      installPhase = ":";
+    };
+
+  /* Like readDir but returning { name, type }
+   */
+  listDir = dir: mapAttrsToList (name: type: { inherit name type; }) (builtins.readDir dir);
+
+
+  /* Like filtersource but only produces a list of paths instead of a source
+   */
+  traverseDirectory = predicate: dir:
+    let
+      recurse = subpath:
+        for (listDir (dir + "/${subpath}")) ({name, type}:
+          let
+            subpath' = "${subpath}${if subpath == "" then "" else "/"}${name}";
+          in
+            for (guard (predicate (dir + "/${subpath'}") type)) ({}:
+              [subpath'] ++
+                for (guard (type == "directory")) (_:
+                  recurse subpath'
+                )
+              )
+        );
+    in
+      recurse ""
+  ;
+
+  traverseNixGitignore = dir: traverseDirectory (gitignoreFilter dir) dir;
+
+  /* Exposed for use *inside* the nix sandbox, called by listingViaNixGitignore.
+   */
+  toStringNixGitignore = dir: concatStringsSep "\n" (traverseNixGitignore dir);
+in
+{
+  inherit makeTest toStringNixGitignore listingViaNixGitignore;
+}