A repo tuned with ObjectHashLower only ever uses lower-case hash
directories, so unlike a bare repo which could have old mixed case
directories, there is no need to do an expensive check of the filesystem in
this case.
I want this as fast as possible, so it can be added to code paths without
slowing them down.
Avoid the set lookup, and rely on laziness,
drops runtime from 14.37 ns to 11.03 ns according to this criterion benchmark:
import Criterion.Main
import qualified Types.Difference as New
import qualified Types.DifferenceOld as Old
main :: IO ()
main = defaultMain
[ bgroup "hasDifference"
[ bench "new" $ whnf (New.hasDifference New.OneLevelObjectHash) new
, bench "old" $ whnf (Old.hasDifference Old.OneLevelObjectHash) old
]
]
where
s = "fromList [ObjectHashLower, OneLevelObjectHash, OneLevelBranchHash]"
new = New.readDifferences s
old = Old.readDifferences s
A little bit of added boilerplate, but I suppose it's worth it to not
need to worry about set lookup overhead. Note that adding more differences
would slow down the old implementation; the new implementation will run
the same speed.
A dead key is both not present at the location that thinks it has a copy,
and also is assumed to probably not be present anywhere else. Although
there may be lurking disconnected repos that somehow still have a copy.
Suprisingly few changes needed for this! This is because the presence log
code only really concerns itself with keys that are present, and dead keys
are not present.
Note that both the location and web log can be parsed as having a dead key.
I don't see any value to having keys listed as dead in the web log, but
since it doesn't change any behavior, there was no point in not parsing it.
