Breaking hard links between repositories

[Guido Ostkamp]

On Tue, 27 May 2008, Matt Cross wrote:
> Is there some file in the repository that will not be hard linked that 
> we can manage the permissions on to prevent pushing?

I the Bryan O'Sullivan's Mercurial book, section 4.5.3 "Concurrent 
access", I found this:

"Mercurial uses locks to ensure that only one process can write to a 
repository at a time (the locking mechanism is safe even over filesystems 
that are notoriously hostile to locking, such as NFS). If a repository is 
locked, a writer will wait for a while to retry if the repository becomes 
unlocked, but if the repository remains locked for too long, the process 
attempting to write will time out after a while. This means that your 
daily automated scripts won't get stuck forever and pile up if a system 
crashes unnoticed, for example. (Yes, the timeout is configurable, from 
zero to infinity.)"

In the code it appears symlinks are used to implement those locks. You 
need to find out where you need to create symlinks to prevent writing to 
the repo. A negative effect would be that if the repo remains locked, all 
applications trying to access the repo get stuck and wait for a timeout.

Also I think it would certainly be possible for you to tweak Mercurial 
code in order to check e.g. presence of write permission for the target 
repo base directory before continuing with the rest of the 'push' code.

RTSL ;-)

Regards

Guido