Re: Question about possible git races

Radoslaw Szkodzinski <astralstorm@o2.pl> writes:

About push vs push, with "really bare git", I take it that you mean two send-pack from remote sites running two receive-pack simultaneously.

There is an explicit race avoidance between the receive-pack processes. When a ref (either branch head or a tag) is updated, it does:

 - read the current value from the ref.
 - do its work.
 - lock to prevent others to create the temporary file for
   updating the ref.
 - create the temporary file for the ref and write the new value.
 - check if the ref's value has not changed from what it
   initially read;
 - rename the temporary file to the ref to unlock.

Read receive-pack.c::update() for exact details if you are interested.

The question does not make any sense for other cases, because branch update by fetch and pull are all scripts based.