Recommendations usability improvements

Core/ModuleInstaller.cs

@@ -1343,12 +1343,21 @@ public bool FindRecommendations(HashSet<CkanModule>
                                                     registry, crit);
             var recommenders = resolver.Dependencies().ToHashSet();
 
+            var checkedRecs = resolver.Recommendations(recommenders)
+                                      .Where(m => resolver.ReasonsFor(m)
+                                                          .Any(r => (r as SelectionReason.Recommended)?.ProvidesIndex == 0))
+                                      .ToHashSet();
+            var conflicting = new RelationshipResolver(toInstall.Concat(checkedRecs), null,
+                                                       RelationshipResolverOptions.ConflictsOpts(),
+                                                       registry, crit)
+                                  .ConflictList.Keys;
+            // Don't check recommendations that conflict with installed or installing mods
+            checkedRecs.ExceptWith(conflicting);
+
             recommendations = resolver.Recommendations(recommenders)
                                       .ToDictionary(m => m,
                                                     m => new Tuple<bool, List<string>>(
-                                                             resolver.ReasonsFor(m)
-                                                                     .Any(r => (r as SelectionReason.Recommended)
-                                                                                   ?.ProvidesIndex == 0),
+                                                             checkedRecs.Contains(m),
                                                              resolver.ReasonsFor(m)
                                                                      .Where(r => r is SelectionReason.Recommended rec
                                                                                  && recommenders.Contains(rec.Parent))

Core/Relationships/RelationshipResolver.cs

@@ -737,6 +737,15 @@ public static RelationshipResolverOptions KitchenSinkOpts()
                 get_recommenders               = true,
             };
 
+        public static RelationshipResolverOptions ConflictsOpts()
+            => new RelationshipResolverOptions()
+            {
+                without_toomanyprovides_kraken = true,
+                proceed_with_inconsistencies   = true,
+                without_enforce_consistency    = true,
+                with_recommends                = false,
+            };
+
         /// <summary>
         /// If true, add recommended mods, and their recommendations.
         /// </summary>