Set the Git fingerprint early

Author: edolstra

src/libfetchers/fetchers.cc

@@ -358,10 +358,10 @@ std::pair<ref<SourceAccessor>, Input> Input::getAccessorUnchecked(const Settings
     try {
         auto [accessor, result] = scheme->getAccessor(settings, store, *this);
 
-        if (!accessor->fingerprint)
-            accessor->fingerprint = result.getFingerprint(store);
+        if (auto fp = accessor->getFingerprint(CanonPath::root).second)
+            result.cachedFingerprint = *fp;
         else
-            result.cachedFingerprint = accessor->fingerprint;
+            accessor->fingerprint = result.getFingerprint(store);
 
         return {accessor, std::move(result)};
     } catch (Error & e) {

src/libfetchers/git-utils.cc

@@ -766,6 +766,7 @@ struct GitSourceAccessor : SourceAccessor
               .options = options,
           }}
     {
+        fingerprint = options.makeFingerprint(rev);
     }
 
     std::string readBlob(const CanonPath & path, bool symlink)