ok op, tracey

Throwing this into the mix for a while, we can always get rid of it again if it becomes annoying. No objections from stsp@

ok stsp@

This allows the main process to avoid looping over all object IDs again in case the pack file used for enumeration is complete. ok op@

The problem that was found in the earlier version has been fixed. ok op@

This implementation marked commits and trees as enumerated before all trees which they depend on were enumerated. This behaviour leads to incomplete pack files when a tree is only partially packed and got-read-pack hits a missing tree entry as a result. The algorithm must be reworked such that packed leave nodes are marked enumerated first, then bubble-up. Found by op@

pointed out by op@

ok op@

The 'nskip' variable is supposed to reflect commits which are waiting on the queue and have the 'skip' color. Only increment 'nskip' when adding such commits to the queue. Problem observed with got send -T and a tag pointing to a deleted branch. Test to reproduce the bug written by op@.

change the three hardcoded seeds to fresh ones generated on demand via arc4random. Suggested/fixed by and ok stsp@

This flag can be expressed as m->reused_delta_offset != 0 because all deltas in valid pack files will be written at a non-zero offset. We allocate a huge number of these structs during packing, so every little bit helps.

With files sorted properly for deltification we produce better deltas but end up consuming more memory and risk running into OpenBSD ulimits during packing. To compensate, reduce the threshold for the amount of delta data we store in memory, spooling more deltas into the cache file. ok op@