Merge branch 'ws/fast-export-with-revision-options'

Use of certain "git rev-list" options with "git fast-export" created nonsense results (the worst two of which being "--reverse" and "--invert-grep --grep=<foo>"). The use of "--first-parent" is made to behave a bit more sensible than before. * ws/fast-export-with-revision-options: fast-export: fix surprising behavior with --first-parent