histedit: correct the number of added revisions in online help
In the context of help document on which this patch focuses, the
example repository, which is source of cloning, should be already
histedit-ed, and contain only 3 revisions (rev # 0 to 2). So, not 3,
but 4 revisions should be added to the destination repository of
cloning, if it contains 7 revisions (rev # 0 to 6).
This patch also adds modifier "histedit-ed" to "example repository",
to make context clear.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.