Status of adding "overlay repositories" to standard Mercurial?

[Brendan Cully]

On Sunday, 25 February 2007 at 16:39, Larry Hastings wrote:
> 
> 
> Brendan Cully wrote a very interesting patch for Mercurial, adding 
> "overlay repositories":
>    http://hg.kublai.com/mercurial/patches/overlay
> If I understand it correctly, when you clone a repository you can tell 
> it to leave all the old revisions in the parent, and the clone will 
> contain only the metadata of those revisions--it won't copy the data 
> proper.  The "overlay" branch acts just like any other branch, except 
> that it must access the parent whenever it needs file data from an 
> "overlay" revision.  (I assume revisions later pulled from the parent 
> are also "overlay" revisions, though I'm not sure.)

Actually, later revisions pulled from the parent are currently copied
into the overlay repository. This wasn't the case previously, but it
was pointed out that the linkrev information in the parent probably
wouldn't match up with the child after the fork. It might still be
possible to keep the _data_ in the parent and only create the _index_
entry in the child, which should be pretty cheap.