amend: add noise in extra to avoid creating obsolescence cycle (
issue3664)
Obsolescence cycle are bad and should be avoided as much as possible. The
current amend implemented touch changeset meta data as few as possible. This
make is easy for amend to result in the same node than a precursors. We add some
deterministic noise in extra to avoid this. In practice, the hex of the amended
changeset is stored in 'amend_source' extra key.
os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
util = <unloaded module 'util'>
util.system = <function system at 0x?>
util = <module 'mercurial.util' from '?'>
util.system = <function system at 0x?>
fred = <unloaded module 're'>
re = <unloaded module 'sys'>
fred = <unloaded module 're'>
fred.sub = <function sub at 0x?>
fred = <proxied module 're'>
re = <unloaded module 'sys'>
re.stderr = <open file '<whatever>', mode 'w' at 0x?>
re = <proxied module 'sys'>