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.
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
verify failed
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
commit failed
diff -r c1fab96507ef a
--- a/a
+++ b/a
@@ -1,1 +1,1 @@ foo
-foo
+barber