Completion updates.
* pb/complete-diff-options: (24 commits)
diff.c: mention completion above add_diff_options
completion: complete --remerge-diff
completion: complete --diff-merges, its options and --no-diff-merges
completion: move --pickaxe-{all,regex} to __git_diff_common_options
completion: complete --ws-error-highlight
completion: complete --unified
completion: complete --output-indicator-{context,new,old}
completion: complete --output
completion: complete --no-stat
completion: complete --no-relative
completion: complete --line-prefix
completion: complete --ita-invisible-in-index and --ita-visible-in-index
completion: complete --irreversible-delete
completion: complete --ignore-matching-lines
completion: complete --function-context
completion: complete --find-renames
completion: complete --find-object
completion: complete --find-copies
completion: complete --default-prefix
completion: complete --compact-summary
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