Lightweight copy

[TK Soh]

On 5/6/07, Matt Mackall <mpm at selenic.com> wrote:
> On Sun, May 06, 2007 at 02:29:03PM +0200, Guido Ostkamp wrote:
> > > The most recent revision of the file or all the files in the directory
> > > is copied, and it remembers where each file was copied from so that it
> > > can merge changes across file renames.
> >
> > thanks, but this is not what I meant.
> >
> > I just did some experiments. My repository (after removal of working copy)
> > has a size of 442 MB. When I "hg copy dir1 dir2; hg commit" where dir1 has
> > everything in it, then (again after removal of the working copy) the size
> > of the repository has increased to 825 MB.
> >
> > This certainly means that Mercurial does not use lightweight copies.
>
> When you copy a file, a new revlog is created with the new filename
> containing a single compressed revision of the file. If the old file
> only had one revision, then yes, the size will double. If the old file
> had a thousand revisions, it will not.

I am guessing a significant portion of renames, especially on the
directories, happen as second thought, so there's a good chance that a
lot of files will only contain one revision. It'd be nice if Hg can
somehow create a link info in the new revlog that reference back to
old revlog instead.