migrate to dotter

configs/fish/functions/_pure_check_availability.fish

@@ -0,0 +1,15 @@
+function _pure_check_availability \
+    --description "Ensure command is available on system" \
+    --argument-names \
+    feature_flag \
+    required_command
+
+    set FAILURE 1
+
+    if not type -q $required_command # command, function or alias are OK
+        echo (set_color $pure_color_warning) \
+            "$feature_flag feature requires: `$required_command`" \
+            (set_color $pure_color_normal)
+        return $FAILURE
+    end
+end