Add support for fish shell when running mk-venv (#425)

* Add support for fish shell

Add $PROVIDERPATH to activate.fish so that people using this shell can
contribute to Checkbox as well.

* Display correct command to run when using fish

* Apply shellcheck suggestions to mk-venv

checkbox-ng/mk-venv

@@ -2,23 +2,29 @@
 
 venv_path=${1:-venv}
 
-venv_path=$(realpath $venv_path)
+venv_path=$(realpath "$venv_path")
 
-if [ -d $venv_path ]; then
+if [ -d "$venv_path" ]; then
     echo "$venv_path already exists"
     exit 1
 fi
 
-virtualenv --quiet --system-site-packages --python=python3 $venv_path
+virtualenv --quiet --system-site-packages --python=python3 "$venv_path"
 
-. $venv_path/bin/activate
+# To prevent https://www.shellcheck.net/wiki/SC1091
+# shellcheck source=/dev/null
+. "$venv_path"/bin/activate
 python3 setup.py develop --quiet | sed -e 's/^/I (develop output) /'
 pip install tqdm psutil
 
 mkdir -p "$venv_path/share/plainbox-providers-1"
-echo "export PROVIDERPATH=$venv_path/share/plainbox-providers-1" >> $venv_path/bin/activate
+echo "export PROVIDERPATH=$venv_path/share/plainbox-providers-1" >> "$venv_path"/bin/activate
+echo "set -gx PROVIDERPATH $venv_path/share/plainbox-providers-1" >> "$venv_path"/bin/activate.fish
 
 echo "virtualenv with an empty provider database created at $venv_path"
 echo "To activate your virtualenv run:"
-echo "$ . $venv_path/bin/activate"
-
+if [ "$(basename "$SHELL")" = "fish" ]; then
+    echo "$ . $venv_path/bin/activate.fish"
+else
+    echo "$ . $venv_path/bin/activate"
+fi