Robust setup env (#1246)

* setup script edits

* substring check is no longer fooled by a venv stored in the benchpark root

* add some explanatory comments

* support only bash and zsh; expand comment

---------

Co-authored-by: pearce8 <pearce8@llnl.gov>

Author: scheibelp

setup-env.sh

@@ -1 +1,25 @@
-export PATH=${PWD}/bin:$PATH
+if [ -n "${BASH_VERSION-}" ]; then
+  _this_file=${BASH_SOURCE[0]}
+elif [ -n "${ZSH_VERSION-}" ]; then
+  eval '_this_file=${(%):-%N}'
+else
+  echo "This script must be sourced from bash or zsh." >&2
+  return 1 2>/dev/null || exit 1
+fi
+# Get abspath
+_this_dir="$(CDPATH= cd -- "$(dirname -- "$_this_file")" 2>/dev/null && pwd -P)"
+
+case ":$PATH:" in
+  *":$_this_dir/bin:"*)
+    # already present: do nothing
+    # This is an exact match, and e.g. won't match if PATH contains this
+    # dir with a trailing slash after "bin". That's good enough to avoid
+    # adding duplicate entries when re-sourcing this, but will add a
+    # duplicate if the user manually added .../bin/ to their PATH
+    :
+    ;;
+  *)
+    PATH="$_this_dir/bin${PATH+:$PATH}"
+    export PATH
+    ;;
+esac