Question

I have a project I cloned over the network to the Mac hard drive (OS X Snow Leopard).

The project is about 1GB in the hard drive

du -s
2073848 .

so when I hg clone proj proj2

then when I

MacBook-Pro ~/development $ du -s proj
2073848 proj

MacBook-Pro ~/development $ du -s proj2
894840  proj2

MacBook-Pro ~/development $ du -s
2397928 .

so the clone seems not so cheap… probably around 400MB… is that so? also, the whole folder grew by about 200MB, which is not the total of proj and proj2 by the way… are there some links and some are not links, that’s why the overlapping is not counted twice?

Answer 1

When possible, Mercurial will use hardlinks on the repository data, it will not use hardlinks on the working directory. Therefore, the only space it can save, is that of the .hg folder.

If you’re using an editor that can break hardlinks, you can cp -al REPO REPOCLONE to use hardlinks on the entire directory, including the working directory, but be aware that it has some caveats. Quoting from the manual:

For efficiency, hardlinks are used for
cloning whenever the source and
destination are on the same filesystem
(note this applies only to the repository data, not to the working
directory). Some filesystems, such as
AFS,
implement hardlinking incorrectly, but do not report errors. In these
cases, use the –pull option to avoid
hardlinking.

In some cases, you can clone repositories and the working directory
using full hardlinks with

$ cp -al REPO REPOCLONE

This is the fastest way to clone, but it is not always safe. The
operation is not atomic (making sure
REPO is not
modified during the operation is up to you) and you have to make sure
your editor breaks hardlinks (Emacs
and most
Linux Kernel tools do so). Also, this is not compatible with certain
extensions that place their metadata
under
the .hg directory, such as mq.