Well, mainly because the data structures supported the notion naturally.
Once you have 0, 1 or 2 parents, the logical progression is "many".
Actually, it's trivial to convert to other SCM's, although I guess the
conversion tools haven't really tried. You can always turn it into a
series of multiple merges. Yes, you lose information, but it's not like
you lose a huge amount.
As to how useful it is.. We don't have a lot of them in the kernel, but I
do have to say that the ones we have generally tend to make perfect sense.
To see just octopus merges, do
git rev-list --parents HEAD |
grep '.* .* .* ' |
git diff-tree --stdin --pretty --always -S |
less -S
but a couple of them are actually fake (same parent listed twice), due to
a confluence of (a) historically bad "git merge" semantics and (b) a bug
that made it not notice. In fact, that bug seems to have re-appeared, now
that I look at it!
Junio: see kernel commits a733a5da9 and 52b097fff89, done as lately as
February of this year. We shouldn't allow that kind of thing, and in git
we have commits b389237ae and 6ea23343ce that were both about those kinds
of mis-uses.
That said, most of those octopus merges look fine and actually give a
nicer view of history. Of course, Len has been known to over-do it a bit ;)
Linus
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