thanks for all the help massaging this diff

patch by Mikhail

This matches actual behaviour of less(1) for Ctrl+u/d, and leaves d/u free for potential future use. Suggested by naddy. Patch by Mark Jamsek

ok tracey

-portable doesn't need this directly.

ok thomas

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

Don't directly include sha1.h as this isn't always in the same location across systems.

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

The SHA implementation is found portably across systems, so don't include sha1.h directly.

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

ok op@

Instead of internally opening and closing the same commit object over and over again, require callers to pass an open commit object in. Avoids an inherent dependency on the commit object cache for reasonable performance. ok op@

This adds support for MacOS (Monteray onward, although should work on older MacOSes). The BSD wrapper for poll/ppoll has been lifted from the work the folks over at OpenSSH have done -- thanks!

ok stsp

Use the same idiom as in the strtonum(3) manpage which produces a more readable error message. OK kn, stsp

ok naddy

Clear the search highlighting when replacing the content of a diff view ('<', '>', '[', ']', 'a', 'w') or a blame view ('b', 'p', 'B'). Previously the position would remain highlighted even if the text there had changed. ok stsp@ or a blame view

ok naddy@

ok naddy tracey

The letter "o" does not overlap with existing options of 'got ref' and is also used by mutt(1) for this purpose.