Hi,
Coming up with a decent way of handling the CRC errors is proving a bit
fiddly :-( We need to not scare the user too much or substantially upset
the operation of normal commands, but also encourage them to fix their
repos. So far I've come up with the following strategy:
gzReadFile in ByteStringUtils detects broken CRCs, and writes to a global
variable to indicate this (adding one more to Darcs.Globals :-( )
Unless Quiet is in the options, Darcs.RunCommand installs an atexit
handler to inspect the global and print out a short message if
appropriate. Something along the lines of "Warning: CRC errors found.
These are probably harmless but should be repaired. Run darcs
<something> for more details."
darcs <something> will check a bunch of files (see below) and also provide
a full explanation of the problem to the user.
It seems like corrupted CRCs might be found in any of
{patches,inventories,pristine.hashed} of any of {the repository we're in,
any other repository involved in a pull/push/get etc,any caches}. I
propose to have a command that checks or repairs just the local repository
+ caches; it makes sense to have to repeat that command on the other
repository if necessary given that it might be on a different
machine/controlled by someone else. When repairing we'd also have to leave
out readonly caches.
The biggest issue I need feedback on now is the appropriate command-line
interface to the check/repair commands. The natural choice would seem to
be to add an option to darcs check and darcs repair. However, this
actually interacts badly with the natural functionality of these two
commands, which is to check/repair the pristine state by replaying the
patch sequence. We shouldn't conflate the two, especially since even check
can cause more patches to be downloaded into a lazy repository. We could
make a 'gzcrcs' option that overrides the other check/repair functionality
completely, but it would seem rather odd anf confusing.
So my current plan is for a completely separate command, darcs gzcrcs
{--check,--repair}. It probably wouldn't be listed in the standard help,
but obviously the short message above would point the user at it.
Thoughts?
Cheers,
Ganesh
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