perf(fs/git): only fetch known or newly requested references

Signed-off-by: George MacRorie <[email protected]>

internal/storage/fs/git/store.go

@@ -3,7 +3,9 @@ package git
 import (
 	"context"
 	"errors"
+	"fmt"
 	"io/fs"
+	"slices"
 	"sync"
 
 	"github.com/go-git/go-git/v5"
@@ -136,7 +138,7 @@ func NewSnapshotStore(ctx context.Context, logger *zap.Logger, url string, opts
 	}
 
 	// do an initial fetch to setup remote tracking branches
-	if _, err := store.fetch(ctx); err != nil {
+	if _, err := store.fetch(ctx, store.snaps.References()); err != nil {
 		return nil, err
 	}
 
@@ -180,8 +182,13 @@ func (s *SnapshotStore) View(ctx context.Context, storeRef storage.Reference, fn
 		return fn(snap)
 	}
 
+	refs := s.snaps.References()
+	if !slices.Contains(refs, ref) {
+		refs = append(refs, ref)
+	}
+
 	// force attempt a fetch to get the latest references
-	if _, err := s.fetch(ctx); err != nil {
+	if _, err := s.fetch(ctx, refs); err != nil {
 		return err
 	}
 
@@ -202,7 +209,7 @@ func (s *SnapshotStore) View(ctx context.Context, storeRef storage.Reference, fn
 // HEAD updates to a new revision, it builds a snapshot and updates it
 // on the store.
 func (s *SnapshotStore) update(ctx context.Context) (bool, error) {
-	if updated, err := s.fetch(ctx); !(err == nil && updated) {
+	if updated, err := s.fetch(ctx, s.snaps.References()); !(err == nil && updated) {
 		// either nothing updated or err != nil
 		return updated, err
 	}
@@ -223,16 +230,23 @@ func (s *SnapshotStore) update(ctx context.Context) (bool, error) {
 	return true, errors.Join(errs...)
 }
 
-func (s *SnapshotStore) fetch(ctx context.Context) (bool, error) {
+func (s *SnapshotStore) fetch(ctx context.Context, heads []string) (bool, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
+	refSpecs := []config.RefSpec{
+		"+refs/tags/*:refs/tags/*",
+	}
+
+	for _, head := range heads {
+		refSpecs = append(refSpecs,
+			config.RefSpec(fmt.Sprintf("+refs/heads/%[1]s:refs/heads/%[1]s", head)),
+		)
+	}
+
 	if err := s.repo.FetchContext(ctx, &git.FetchOptions{
-		Auth: s.auth,
-		RefSpecs: []config.RefSpec{
-			"+refs/heads/*:refs/heads/*",
-			"+refs/tags/*:refs/tags/*",
-		},
+		Auth:     s.auth,
+		RefSpecs: refSpecs,
 	}); err != nil {
 		if !errors.Is(err, git.NoErrAlreadyUpToDate) {
 			return false, err

internal/storage/fs/git/store_test.go

@@ -172,7 +172,7 @@ flags:
 	require.NoError(t, fi.Close())
 
 	// commit changes
-	_, err = tree.Commit("chore: update features.yml", &git.CommitOptions{
+	_, err = tree.Commit("chore: update features.yml add foo and bar", &git.CommitOptions{
 		All:    true,
 		Author: &object.Signature{Email: "[email protected]", Name: "dev"},
 	})
@@ -185,18 +185,6 @@ flags:
 		RefSpecs:   []config.RefSpec{"refs/heads/new-branch:refs/heads/new-branch"},
 	}))
 
-	// wait until the snapshot is updated or
-	// we timeout
-	select {
-	case <-ch:
-	case <-time.After(time.Minute):
-		t.Fatal("timed out waiting for snapshot")
-	}
-
-	require.NoError(t, err)
-
-	t.Log("received new snapshot")
-
 	require.NoError(t, store.View(ctx, "", func(s storage.ReadOnlyStore) error {
 		_, err := s.GetFlag(ctx, storage.NewResource("production", "bar"))
 		require.Error(t, err, "flag should not be found in default revision")
@@ -209,11 +197,65 @@ flags:
 		return nil
 	}))
 
+	// should be able to fetch flag from previously unfetched reference
 	require.NoError(t, store.View(ctx, "new-branch", func(s storage.ReadOnlyStore) error {
 		_, err := s.GetFlag(ctx, storage.NewResource("production", "bar"))
 		require.NoError(t, err, "flag should be present on new-branch")
 		return nil
 	}))
+
+	// flag bar should not yet be present
+	require.NoError(t, store.View(ctx, "new-branch", func(s storage.ReadOnlyStore) error {
+		_, err := s.GetFlag(ctx, storage.NewResource("production", "baz"))
+		require.Error(t, err, "flag should not be found in explicitly named new-branch revision")
+		return nil
+	}))
+
+	// update features.yml, now with the bar flag
+	fi, err = workdir.OpenFile("features.yml", os.O_TRUNC|os.O_RDWR, os.ModePerm)
+	require.NoError(t, err)
+
+	updated = []byte(`namespace: production
+flags:
+  - key: foo
+    name: Foo
+  - key: bar
+    name: Bar
+  - key: baz
+    name: Baz`)
+
+	_, err = fi.Write(updated)
+	require.NoError(t, err)
+	require.NoError(t, fi.Close())
+
+	// commit changes
+	_, err = tree.Commit("chore: update features.yml add baz", &git.CommitOptions{
+		All:    true,
+		Author: &object.Signature{Email: "[email protected]", Name: "dev"},
+	})
+	require.NoError(t, err)
+
+	// push new commit
+	require.NoError(t, repo.Push(&git.PushOptions{
+		Auth:       &http.BasicAuth{Username: "root", Password: "password"},
+		RemoteName: "origin",
+		RefSpecs:   []config.RefSpec{"refs/heads/new-branch:refs/heads/new-branch"},
+	}))
+
+	// we should expect to see a modified event now because
+	// the new reference should be tracked
+	select {
+	case <-ch:
+	case <-time.After(time.Minute):
+		t.Fatal("timed out waiting for fetch")
+	}
+
+	// should be able to fetch flag bar now that it has been pushed
+	require.NoError(t, store.View(ctx, "new-branch", func(s storage.ReadOnlyStore) error {
+		_, err := s.GetFlag(ctx, storage.NewResource("production", "baz"))
+		require.NoError(t, err, "flag should be present on new-branch")
+		return nil
+	}))
 }
 
 func Test_Store_View_WithSemverRevision(t *testing.T) {