narrow: read pending file when applicable

Now that this is part of the transaction, this is necessary to make sure we read
the right data in hooks (if any).

mercurial/narrowspec.py

@@ -16,6 +16,7 b' from . import ('
     mergestate as mergestatemod,
     scmutil,
     sparse,
+    txnutil,
     util,
 )
 
@@ -169,7 +170,13 b' def parseconfig(ui, spec):'
 def load(repo):
     # Treat "narrowspec does not exist" the same as "narrowspec file exists
     # and is empty".
-    spec = repo.svfs.tryread(FILENAME)
+    spec = None
+    if txnutil.mayhavepending(repo.root):
+        pending_path = b"%s.pending" % FILENAME
+        if repo.svfs.exists(pending_path):
+            spec = repo.svfs.tryread(FILENAME)
+    if spec is None:
+        spec = repo.svfs.tryread(FILENAME)
     return parseconfig(repo.ui, spec)