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@

Saves us from doing a malloc/free call for every item on the list. ok op@

imsg_clear frees and closes resources allocated as part of enqueueing imsgs so it's a no-op after reads. discussed with and ok stsp@

tested by thomas, naddy, and myself

millert@ suggests that this check is not needed, and that ideally we should be using close-on-exec instead. I will look into this, but in the meantime this change will help -portable: https://bugs.gentoo.org/828003

This adds the capability to compile got-portable on FreeBSD.

This commit modifies the GoT main branch to be able to compile it under linux.

Feature requested by naddy. ok naddy, who also suggested some tweaks that will arrive shortly

Known to work against git-daemon and github Git server implementations. Tests by abieber, naddy, jrick, and myself. Man page additions reviewed by Lucas.

This saves an iteration over the entire h->offsets array when opening a pack index which should not contain large offsets in the first place. ok millert@

The singly-linked tail queue macros were added to OpenBSD 6.9 and are more widely available on other systems. ok stsp

This way, the size of a raw object is the same regardless of whether the object was found in a loose object file or in a pack file.

Avoids an error where tog(1) would exit with "poll: Interrupted system call" while the terminal window was being resized. ok millert