MountedInputAccessor, FilteringInputAccessor: Respect the path display prefix/suffix

This was causing Git paths not to be rendered correctly.

src/libfetchers/filtering-input-accessor.cc

@@ -38,7 +38,7 @@ std::string FilteringInputAccessor::readLink(const CanonPath & path)
 
 std::string FilteringInputAccessor::showPath(const CanonPath & path)
 {
-    return next->showPath(prefix / path);
+    return displayPrefix + next->showPath(prefix / path) + displaySuffix;
 }
 
 void FilteringInputAccessor::checkAccess(const CanonPath & path)

src/libfetchers/filtering-input-accessor.hh

@@ -27,7 +27,9 @@ struct FilteringInputAccessor : InputAccessor
         : next(src.accessor)
         , prefix(src.path)
         , makeNotAllowedError(std::move(makeNotAllowedError))
-    { }
+    {
+        displayPrefix.clear();
+    }
 
     std::string readFile(const CanonPath & path) override;
 

src/libfetchers/mounted-input-accessor.cc

@@ -9,6 +9,8 @@ struct MountedInputAccessor : InputAccessor
     MountedInputAccessor(std::map<CanonPath, ref<InputAccessor>> _mounts)
         : mounts(std::move(_mounts))
     {
+        displayPrefix.clear();
+
         // Currently we require a root filesystem. This could be relaxed.
         assert(mounts.contains(CanonPath::root));
 
@@ -48,7 +50,7 @@ struct MountedInputAccessor : InputAccessor
     std::string showPath(const CanonPath & path) override
     {
         auto [accessor, subpath] = resolve(path);
-        return accessor->showPath(subpath);
+        return displayPrefix + accessor->showPath(subpath) + displaySuffix;
     }
 
     std::pair<ref<InputAccessor>, CanonPath> resolve(CanonPath path)