Merge branch 'bh/diff-highlight-graph' into maint

"diff-highlight" script (in contrib/) learned to work better with "git log -p --graph" output. * bh/diff-highlight-graph: diff-highlight: avoid highlighting combined diffs diff-highlight: add multi-byte tests diff-highlight: ignore test cruft diff-highlight: add support for --graph output diff-highlight: add failing test for handling --graph output diff-highlight: add some tests