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

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

ok millert, naddy

Make use of this in 'got clone' to persist -R option arguments given on the command line in the cloned repository's got.conf(5) file.

Set fetch-all-branches in the got.conf(5) file created by 'got clone -a' in order to make a future 'got fetch' act like 'got fetch -a' by default.

ok millert

ok tracey