Added nix-shell plugin to oh-my-zsh

pkgs/zsh/plugins/nix-shell/nix-shell.plugin.zsh

@@ -0,0 +1,82 @@
+
+NIX_SHELL_PLUGIN_DIR=${0:a:h}
+
+which bash > /dev/null 2>&1
+if [ "$?" -ne "0" ]; then
+  echo
+  echo "  WARNING: bash is not installed."
+  echo "  for zsh-nix-shell to work bash has to be in PATH"
+  echo
+fi
+
+
+# extracts packages argument from args and passes them in $NIX_SHELL_PACKAGES variable.
+function nix-shell() {
+  local -a ARGS; ARGS=("$@")
+  local NIX_SHELL_PACKAGES="${NIX_SHELL_PACKAGES}"
+
+  # extract -p|--packages argument into NIX_SHELL_PACKAGES
+  local IN_PACKAGES=0
+  local PURE=0
+  while [[ ${#ARGS[@]} -gt 0 ]]
+  do
+    key=${ARGS[1]}
+    # enter "--packages packages..." mode
+    if [[ $key = "-p" || $key = "--packages" ]]
+    then
+      IN_PACKAGES=1
+      NIX_SHELL_PACKAGES+=${NIX_SHELL_PACKAGES:+ }${ARGS[2]}
+      ARGS=("${ARGS[@]:1}")
+
+    # skip "--arg name value" argument
+    elif [[ $key = "--arg" ]]
+    then
+      IN_PACKAGES=0
+      ARGS=("${ARGS[@]:2}")
+
+    elif [[ $key = "--pure" ]]
+    then
+      PURE=1
+
+    # skip all other unary arguments
+    elif [[ $key == "-"* ]]
+    then
+      IN_PACKAGES=0
+      ARGS=("${ARGS[@]:1}")
+
+    # If we don't have any argument prefix we are either in package mode
+    # or we have encountered the path argument
+    elif [[ $IN_PACKAGES = 1 ]]
+    then
+      NIX_SHELL_PACKAGES+=" $key"
+    fi
+    ARGS=("${ARGS[@]:1}")
+  done
+
+  # call real nix shell
+  if [[ $PURE = 1 ]]
+  then
+    # if you use --pure you get bash
+    command nix-shell "$@"
+  else
+    NIX_EXECUTING_SHELL=$(readlink -f /proc/$$/exe)
+    if [[ -z "$NIX_EXECUTING_SHELL" ]] && command -v lsof &> /dev/null
+    then
+      NIX_EXECUTING_SHELL=$(lsof -p $$ | awk '$4=="txt" {print $9}' | head -n 1)
+    fi
+    if [[ -z "$NIX_EXECUTING_SHELL" ]] && command -v zsh &> /dev/null
+    then
+      NIX_EXECUTING_SHELL="zsh"
+    fi
+    if [[ -z "$NIX_EXECUTING_SHELL" ]]
+    then
+      echo "could not determine executing shell. please install `lsof` or `zsh` directly to your PATH"
+      echo "If this error persists create an issue at https://github.com/chisui/zsh-nix-shell/issues/new/choose"
+      return 1
+    fi
+    NIX_SHELL_PACKAGES="$NIX_SHELL_PACKAGES" \
+    NIX_BUILD_SHELL="$NIX_SHELL_PLUGIN_DIR/scripts/buildShellShim" \
+    NIX_EXECUTING_SHELL=$NIX_EXECUTING_SHELL \
+    command nix-shell "$@"
+  fi
+}