Efficiently comparing manifests

[Benoit Boissinot]

On Thu, May 13, 2010 at 9:27 PM, Matt Mackall <mpm at selenic.com> wrote:
> On Thu, 2010-05-13 at 15:11 -0400, Greg Ward wrote:
>> On Thu, May 13, 2010 at 3:02 PM, Matt Mackall <mpm at selenic.com> wrote:
>> > On Thu, 2010-05-13 at 14:44 -0400, Greg Ward wrote:
>>
>> But dummy merges add an entry to the manifest log: new entry, new node
>> ID, same content as first parent.
>
> Ahh, right. That may or may not be a bug.
>
probably a bug, as we "fix" this case for filelogs.

> If you want to be clever, you can still get away with doing half the
> work:
>
> m = manifest.read(node)
> h = hash(m, otherp1, otherp2) # calculate the hash assuming unchanged
> return h == other

or:
m = manifest.read(node)
manifest.cmp(other, m)
(which does the hash trick)

but in general the slowness can happen because the manifest are read
in the "wrong" order. It's always interesting to check order.

regards,

Benoit