+#!/bin/sh
+
+set -e
+
+repo_dir="`mktemp -d`"
+repo="$repo_dir/repo"
+git init "$repo"
+(
+ cd "$repo"
+ echo Contents > test-file
+ git add test-file
+ git commit -m 'Commit message'
+)
+
+conf="`mktemp`"
+cat > "$conf" <<EOF
+[foo]
+git_repo = file://$repo
+git_ref = master
+EOF
+
+python3 ./pinch.py pin "$conf"
+
+(
+ cd "$repo"
+ echo Other contents > other-file
+ git add other-file
+ git commit -m 'Second commit message'
+)
+
+python3 ./pinch.py pin "$conf"
+
+actual_env_command=`python3 ./pinch.py update --dry-run "$conf"`
+
+rm -rf "$repo_dir" "$conf"
+
+expected_env_command_RE='^nix-env --profile /nix/var/nix/profiles/per-user/[^/]+/channels --show-trace --file '\''<nix/unpack-channel.nix>'\'' --install --from-expression '\''f: f \{ name = "(repo-[0-9]{10}-[0-9a-f]{11})"; channelName = "foo"; src = builtins.storePath "/nix/store/.{32}-\1.tar.xz"; \}'\''$'
+
+if echo "$actual_env_command" | egrep "$expected_env_command_RE" > /dev/null;then
+ echo PASS
+else
+ echo "Output: $actual_env_command"
+ echo "does not match RE: $expected_env_command_RE"
+ exit 1
+fi