Bugfix to follow symlink when stat'ing file for HEAD retrieval.

Also avoid using Lstat to reduce potential for confusion when the only
(purported) advantage is for efficiency by reducing a few steps of indirection.

handlers.go

@@ -534,7 +534,7 @@ func newRetrieveFileHandler(db *sql.DB) func(http.ResponseWriter, *http.Request)
             return
         }
 
-        info, err := os.Lstat(path) // intential Lstat() to avoid unnecessary link following.
+        info, err := os.Stat(path)
         if err != nil {
             if errors.Is(err, os.ErrNotExist) {
                 err = newHttpError(http.StatusNotFound, errors.New("path does not exist"))

list.go

@@ -93,7 +93,7 @@ func listMetadata(dir string, base_names []string) (map[string]fs.FileInfo, []st
                 return fs.SkipDir
             }
 
-            _, err := os.Lstat(filepath.Join(path, ".SewerRatignore"))
+            _, err := os.Stat(filepath.Join(path, ".SewerRatignore"))
             if err != nil && errors.Is(err, fs.ErrNotExist) {
                 return nil
             } else {
@@ -114,6 +114,8 @@ func listMetadata(dir string, base_names []string) (map[string]fs.FileInfo, []st
             // our index, so that the index is updated when the target is changed
             // (rather than when the link itself is changed).
             info, err = os.Stat(path)
+
+            // We don't recurse into symlinked directories, though.
             if err == nil && info.IsDir() {
                 return nil
             }

load_test.go

@@ -84,7 +84,7 @@ func TestLoadMetadata(t *testing.T) {
             t.Fatalf("failed to create a symlink; %v", err)
         }
 
-        info, err := os.Lstat(path) // check that symlinks are correctly loaded.
+        info, err := os.Stat(path)
         if err != nil {
             t.Fatal(err)
         }

verify.go

@@ -48,7 +48,7 @@ func (vr *verificationRegistry) Provision(path string) (string, error) {
 
         candidate = ".sewer_" + base64.RawURLEncoding.EncodeToString(buff)
 
-        _, err = os.Lstat(filepath.Join(path, candidate)) // intential Lstat() to avoid unnecessary link following.
+        _, err = os.Stat(filepath.Join(path, candidate))
         if err != nil {
             if errors.Is(err, os.ErrNotExist) {
                 found = true