largefiles: use util.readfile in overrides

hgext/largefiles/overrides.py

@@ -967,16 +967,7 b' def overridearchive(orig, repo, dest, no'
 
             f = lfutil.splitstandin(f)
 
-            def getdatafn():
-                fd = None
-                try:
-                    fd = open(path, 'rb')
-                    return fd.read()
-                finally:
-                    if fd:
-                        fd.close()
-
-            getdata = getdatafn
+            getdata = lambda: util.readfile(path)
         write(f, 'x' in ff and 0o755 or 0o644, 'l' in ff, getdata)
 
     if subrepos:
@@ -1024,16 +1015,7 b' def hgsubrepoarchive(orig, repo, archive'
 
             f = lfutil.splitstandin(f)
 
-            def getdatafn():
-                fd = None
-                try:
-                    fd = open(os.path.join(prefix, path), 'rb')
-                    return fd.read()
-                finally:
-                    if fd:
-                        fd.close()
-
-            getdata = getdatafn
+            getdata = lambda: util.readfile(os.path.join(prefix, path))
 
         write(f, 'x' in ff and 0o755 or 0o644, 'l' in ff, getdata)