User-visible changes:
- tog: extend log view author highlight colour to full field width
- tog: make headline highlight extend the full view width
- tog: add new log view limit feature to filter commits
- tog: respect current cursor position during log search
- tog: implement runtime help accessible via H,F1 keymaps
- add gotadmin init -b <branch> to specify repo head ref
- ensure got patch respects x-bit perms for new files
- show file mode for new added files in work tree diffs
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