It's only a preparatory step, as checking whether a size_t is less than SIZE_MAX is moot. In a follow-up commit, however, the `filesize' field of the struct got_pack will become off_t and these checks will kick in. This also makes consistent how we guard mmap(2) against empty files. ok and improvements stsp@

ok millert@

ok stsp@

ok op, tracey

The old code did not work correctly if only a single object Id was to be sent to got-read-pack. Make got-read-pack error out if the list of commits for object enumeration is empty to catch this problem if it occurs again. Found by the send_basic test, which was failing with GOT_TEST_PACK=1 ok tracey

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@

Fixes an error where got-read-pack errors out with "bad object data" during 'got send' because we ended up handing a tag object to the commit object parser.

ok op@

This approach uses more memory but is much faster. To offset the additional memory usage somewhat the cache now stores very small deltas only. However, overall memory usage goes up. Hopefully we will find a way to reduce this later. ok op@