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

Additional testing by Thomas Adam. ok tracey

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

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

This will eventually be used by 'gotadmin pack'. Checksum init and finalization will need to be done by the caller since many objects will be written out in compressed form while we are computing checksums across the entire pack file. ok millert, naddy

ok millert, naddy

ok millert, naddy

ok stsp

Cast printf arguments of type time_t and off_t to long long to match the %lld format specifier on platforms where this might not be the case. In parse.y, switch the number variable to long long because all its interactions are with that type anyway. ok millert stsp

If a merged commit wants to delete a locally added file, and this locally added file matches the content which was deleted in the commit being merged, we can go ahead with the deletion because there is no risk of data loss. fixes the histedit problem reported by jrick on freenode

approach suggested by ori@ and matches how git9 behaves ok semarie@ (who can now work with Rust-related Git repos containing submodules)

semarie@ reported an error from go-git used by Cirrus CI: "57243613255d758e15b0f5ae1c960b970f0435f8: malformed mode (0100640)!" 'git fsck' has no problem with mode 0100640. But writing just the two most commonly used file modes should provide the best compatibility.

Trim leading and trailing whitespace from log messages when creating commits. Fixes a rebase issue but should be a good idea in general.