write-text: remove support for copy

This is a huge anti‐declarative footgun; `copy` files cannot
distinguish if a previous version is managed by nix-darwin, so they
can’t check the hash, so they’re prone to destroying data, and
copied files are not deleted when they’re removed from the system
configuration, which led to a security bug. Nothing else in‐tree
was using this functionality, so let’s make sure it doesn’t
cause any more bugs.

modules/lib/write-text.nix

@@ -45,14 +45,6 @@ in
  '';
  };
 
- copy = mkOption {
- type = types.bool;
- default = false;
- description = ''
- Whether this file should be copied instead of symlinking.
- '';
- };
-
  knownSha256Hashes = mkOption {
  internal = true;
  type = types.listOf types.str;

modules/system/etc.nix

@@ -10,7 +10,6 @@ let
  };
 
  etc = filter (f: f.enable) (attrValues config.environment.etc);
- etcCopy = filter (f: f.copy) (attrValues config.environment.etc);
 
 in
 
@@ -34,9 +33,10 @@ in
  ''
  mkdir -p $out/etc
  cd $out/etc
- ${concatMapStringsSep "\n" (attr: "mkdir -p $(dirname '${attr.target}')") etc}
- ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") etc}
- ${concatMapStringsSep "\n" (attr: "touch '${attr.target}'.copy") etcCopy}
+ ${concatMapStringsSep "\n" (attr: ''
+ mkdir -p "$(dirname ${escapeShellArg attr.target})"
+ ln -s ${escapeShellArgs [ attr.source attr.target ]}
+ '') etc}
  '';
 
  system.activationScripts.etcChecks.text = ''
@@ -55,10 +55,6 @@ in
  etcStaticFile=/etc/static/$subPath
  etcFile=/etc/$subPath
 
- if [[ -e $configFile.copy ]]; then
- continue
- fi
-
  # We need to check files that exist and aren't already links to
  # $etcStaticFile for known hashes.
  if [[
@@ -109,11 +105,6 @@ in
  mkdir -p "$etcDir"
  fi
 
- if [[ -e $etcStaticFile.copy ]]; then
- cp "$etcStaticFile" "$etcFile"
- continue
- fi
-
  if [[ -e $etcFile ]]; then
  if [[ $(readlink -- "$etcFile") == "$etcStaticFile" ]]; then
  continue
@@ -130,7 +121,7 @@ in
 
  # Delete stale links into /etc/static.
  if [[
- $(readlink "$etcFile") == "$etcStaticFile"
+ $(readlink -- "$etcFile") == "$etcStaticFile"
  && ! -e $etcStaticFile
  ]]; then
  rm "$etcFile"