feat: optimize git walker

Signed-off-by: Brian McGee <[email protected]>

walk/git.go

@@ -2,13 +2,12 @@ package walk
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"io/fs"
+	"os"
 	"path/filepath"
 
 	"github.com/charmbracelet/log"
-	"github.com/go-git/go-git/v5/plumbing/format/index"
 
 	"github.com/go-git/go-git/v5"
 )
@@ -39,9 +38,57 @@ func (g *gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 		return fmt.Errorf("failed to open git index: %w", err)
 	}
 
+	// cache in-memory whether a path is present in the git index
+	var cache map[string]bool
+
 	for path := range g.paths {
 
-		err = filepath.Walk(path, func(path string, info fs.FileInfo, err error) error {
+		if path == g.root {
+			// we can just iterate the index entries
+			for _, entry := range idx.Entries {
+				select {
+				case <-ctx.Done():
+					return ctx.Err()
+				default:
+					path := filepath.Join(g.root, entry.Name)
+
+					// stat the file
+					info, err := os.Lstat(path)
+
+					file := File{
+						Path:    path,
+						RelPath: relPathFn(path),
+						Info:    info,
+					}
+
+					if err = fn(&file, err); err != nil {
+						return err
+					}
+				}
+			}
+			continue
+		}
+
+		// otherwise we ensure the git index entries are cached and then check if they are in the git index
+		if cache == nil {
+			cache = make(map[string]bool)
+			for _, entry := range idx.Entries {
+				cache[entry.Name] = true
+			}
+		}
+
+		relPath, err := filepath.Rel(g.root, path)
+		if err != nil {
+			return fmt.Errorf("failed to find relative path for %v: %w", path, err)
+		}
+
+		_, ok := cache[relPath]
+		if !(path == g.root || ok) {
+			log.Debugf("path %v not found in git index, skipping", path)
+			continue
+		}
+
+		return filepath.Walk(path, func(path string, info fs.FileInfo, err error) error {
 			if info.IsDir() {
 				return nil
 			}
@@ -51,9 +98,8 @@ func (g *gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 				return err
 			}
 
-			if _, err = idx.Entry(relPath); errors.Is(err, index.ErrEntryNotFound) {
-				// we skip this path as it's not staged
-				log.Debugf("Path not found in git index, skipping: %v, %v", relPath, path)
+			if _, ok := cache[relPath]; !ok {
+				log.Debugf("path %v not found in git index, skipping", path)
 				return nil
 			}
 
@@ -65,10 +111,6 @@ func (g *gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 
 			return fn(&file, err)
 		})
-		if err != nil {
-			return err
-		}
-
 	}
 
 	return nil