changegroup: call 'prechangegroup' hook before setting up write delay The 'prechangegroup' interfere with 'delayupdate' logic because it trigger the one time call of 'changelog._writepending' (see issure4934). There is no reason not to call that hook before setting up 'delayupdate' so we move the call a bit earlier to avoid interference.

changegroup: fix the scope of a try finally The try finally is here to ensure we release the just-created transaction. Therefore we should not do half a dozen operations before actually entry the try scope.

encoding: re-escape U+DCxx characters in toutf8b input (issue4927) This is the final missing piece in fully round-tripping random byte strings through UTF-8b. While this issue means that UTF-8 <-> UTF-8b isn't fully bijective, we don't expect to ever see U+DCxx codepoints in "real" UTF-8 data, so it should remain bijective in practice.

encoding: use getutf8char in toutf8b This correctly avoids the ambiguity of U+FFFD already present in the input and similar confusion by working a character at a time.