Merge with stable

.hgsigs

@@ -200,3 +200,4 @@
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+f62bb5d07848ca598aa860a517394130b61bf2ee 0 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

.hgtags

@@ -260,3 +260,4 @@
 c89f98051a56f4e2e3ea51e7e56eb2d4f7301178 5.4.2-vms
 28163c5de797e5416f9b588940f4608269b4d50a 5.5rc0
 7fc3c5fbc65f6fe85d70ea63923b8767dda4f2e0 5.5
+f62bb5d07848ca598aa860a517394130b61bf2ee 5.5.1

mercurial/keepalive.py

@@ -542,4 +542,6 @@
             return line
 
         # No newline in local buffer. Read until we find one.
+        # readinto read via readinto will already return _rbuf
+        if self._raw_readinto is None:
             chunks = [self._rbuf]
@@ -545,4 +547,6 @@
             chunks = [self._rbuf]
+        else:
+            chunks = []
         i = -1
         readsize = self._rbufsize
         while True:

tests/test-check-format.t

-#require black
+#require black test-repo
 
   $ cd $RUNTESTDIR/..
   $ black --config=black.toml --check --diff `hg files 'set:(**.py + grep("^#!.*python")) - mercurial/thirdparty/**'`