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@

in this case they're luckily the same; got_imsg_object_idlist and got_imsg_reused_delta only have one size_t long field. ok stsp@

use correct error code and ok stsp@

Simplifies the reading of the author/committer string and makes also the code shorter. ok stsp@

recv_imsg_error already checks the size of the message, and it does so more precisely than the removed code. ok stsp@

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@

ok op@

imsg_read() will call recvmsg() on the file descriptor regardless of the read buffer's state, so we should ensure that data is ready. The read buffer is used by imsg_get(), not imsg_read(). We already call imsg_get() before imsg_read(), and call the latter only if imsg_get() returns zero.

This speeds up loading of trees significantly. ok op@

Avoids some extra malloc/free in a performance-critical path. ok op@

no functional change

This significantly speeds up the deltification step of packing by avoiding imsg traffic. gotadmin no longer requests individual raw deltas from got-read-pack to check whether it can reuse them. Instead, got-read-pack obtains a list of objects we want to pack, and hands back the list of all deltas in its pack file which can be reused. Messages are now batched such that imsg buffers are filled as much as possible. Another advantage is that deltas we are not going to reuse will no longer be written to the delta cache file, saving disk space. Before this patch, any raw delta candidate was written to the delta cache file by got-read-pack, and the decision whether to reuse the delta happened afterwards in the gotadmin process. Code for reading individual raw deltas is now unused and could be removed at some point. ok op@

This reduces memory and disk space consumption during packing. with tweaks + memleak on error fix from op@ ok op@