Update convert help text
Add Mercurial as a source format, clarify that the include directive triggers the exclusion of all not explicitely included files/dirs and use MAPFILE instead of revmapfile in the text, following the short message convention.
#!/bin/sh
hg init a
cd a
echo bar > foo
hg add foo
hg ci -m 'add foo' -d '1000000 0'
echo foobar > foo
hg ci -m 'change foo' -d '1000001 0'
echo 'quiet:'
hg --quiet diff -r 0 -r 1
echo
echo 'normal:'
hg diff -r 0 -r 1
echo
echo 'verbose:'
hg --verbose diff -r 0 -r 1
echo
echo 'debug:'
hg --debug diff -r 0 -r 1
echo