From 6118a3f382d9e136575da6a64a444af08eef2363 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Wed, 19 Feb 2020 14:57:11 +0100
Subject: Add some flags to persistent-nix-shell wrapper

---
 pkgs/persistent-nix-shell/default.nix             | 13 +----------
 pkgs/persistent-nix-shell/persistent-nix-shell.sh | 27 +++++++++++++++++++++++
 2 files changed, 28 insertions(+), 12 deletions(-)
 create mode 100644 pkgs/persistent-nix-shell/persistent-nix-shell.sh

diff --git a/pkgs/persistent-nix-shell/default.nix b/pkgs/persistent-nix-shell/default.nix
index 8a74eb4..5e53ee6 100644
--- a/pkgs/persistent-nix-shell/default.nix
+++ b/pkgs/persistent-nix-shell/default.nix
@@ -5,16 +5,5 @@ pkgs.writeTextFile {
   executable  = true;
   destination = "/bin/persistent-nix-shell";
 
-  text = ''
-    #!/bin/sh -eu
-
-    mkdir -p .gcroots
-
-    nix-instantiate shell.nix --indirect --add-root $PWD/.gcroots/shell.drv > /dev/null
-    nix-store -r $(nix-store --query --references $PWD/.gcroots/shell.drv) --indirect --add-root $PWD/.gcroots/shell.dep > /dev/null
-
-    # Fix to prevent implicit interactiveBash dependency
-    export NIX_BUILD_SHELL=/run/current-system/sw/bin/bash
-    exec nix-shell $(readlink $PWD/.gcroots/shell.drv) "$@"
-  '';
+  text = builtins.readFile ./persistent-nix-shell.sh;
 }
diff --git a/pkgs/persistent-nix-shell/persistent-nix-shell.sh b/pkgs/persistent-nix-shell/persistent-nix-shell.sh
new file mode 100644
index 0000000..b9ecfbc
--- /dev/null
+++ b/pkgs/persistent-nix-shell/persistent-nix-shell.sh
@@ -0,0 +1,27 @@
+#!/bin/sh -eu
+
+mkdir -p .gcroots
+
+inherit_shell=''
+update=''
+
+while getopts 'su' flag; do
+	case "${flag}" in
+		s) inherit_shell='true' ;;
+		u) update='true' ;;
+	esac
+done
+
+if [[ ! -f "$PWD/.gcroots/shell.drv" || $update ]]; then
+	nix-instantiate shell.nix --indirect --add-root $PWD/.gcroots/shell.drv > /dev/null
+	nix-store -r $(nix-store --query --references $PWD/.gcroots/shell.drv) --indirect --add-root $PWD/.gcroots/shell.dep > /dev/null
+fi
+
+# Fix to prevent implicit interactiveBash dependency
+export NIX_BUILD_SHELL=/run/current-system/sw/bin/bash
+
+if [ $inherit_shell ]; then
+	exec nix-shell $(readlink $PWD/.gcroots/shell.drv) --command $SHELL
+else
+	exec nix-shell $(readlink $PWD/.gcroots/shell.drv)
+fi
-- 
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