Re: git clone questions relating to cpio

From: Johan Herland <johan@herland.net>
Date: Oct 1, 2007, 21:42 UTC
Message-ID: <200710012342.37352.johan@herland.net>
In-Reply-To: <3f4fd2640710011228w61ce34b5ve47ea529eed384fd@mail.gmail.com>

On Monday 01 October 2007, Reece Dunn wrote:

Show 7 quoted lines

> Hi,
> 
> I am running a Linux From Scratch 6.2 system that does not have cpio
> installed on it. This means that I can't clone a local repository
> unless I install cpio. Is it possible to use a fallback method if cpio
> is not present, as there is no NO_CPIO option on make like there is
> for OpenSSH, cURL and expat?

Using "file://" when specifying the source repo will force git-clone to use the git protocol, instead of doing a copy/hardlink.

I.e. change "git clone foo bar" to "git clone file://foo bar" in order to prevent git-clone from calling cpio.

However, grepping for cpio in the git source tree reveals a couple of uses in git-merge, so you might bump into problems there...

> Also, I have an external USB hardrive that is mounted onto the virtual
> filesystem. Will clones from the USB harddrive (or a USB flash drive
> that is mounted) result in a copy being performed, not a hardlink?

Hardlinks are impossible across filesystems. If you're cloning to a different filesystem git will _have_ to make a full copy.

> Ideally, the hard linking for local clones should be optional.

<quote src="git-clone(1)"> --local, -l

  When the repository to clone from is on a local machine, this flag 
bypasses normal "git aware" transport mechanism and clones the repository 
by making a copy of HEAD and everything under objects and refs directories. 
The files under .git/objects/ directory are hardlinked to save space when 
possible. This is now the default when the source repository is specified 
with /path/to/repo syntax, so it essentially is a no-op option. To force 
copying instead of hardlinking (which may be desirable if you are trying to 
make a back-up of your repository), but still avoid the usual "git aware" 
transport mechanism, --no-hardlinks can be used.

--no-hardlinks

  Optimize the cloning process from a repository on a local filesystem by 
copying files under .git/objects directory.
</quote>

And as I said above, you can use "file://" to force the "git aware" transport mechanism, which bypasses the whole local copy/hardlink issue entirely.

> What if I want to move a repository because, for example, I have imported
> a CVS repository and now want to push it to a new bare repository?

Even if you were to use hardlinks, cloning a repo followed by deleting the original will be safe (as long as you don't supply '--shared' to git-clone). That's the beauty of hardlinks.

I also think it's fairly safe to just 'mv' the whole repository to its new location.

Have fun! :)

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net