Retrospectively add alternates to a repository?

Hi,

I have a local mirror of a remote repository (to save time
cloning over a slow network).  But before I created the
local mirror I already cloned the remote repo directly.

Is it possible to retrospectively add an alternates spec
to this local repository (the equivalent of doing what 
--reference does during the clone)?

Thanks for any help.

Regards,
Steve

Hi,

On Sat, Feb 27, 2010 at 7:54 AM, Steve Folly [off-list ref] wrote:

I have a local mirror of a remote repository (to save time
cloning over a slow network).  But before I created the
local mirror I already cloned the remote repo directly.

Is it possible to retrospectively add an alternates spec
to this local repository (the equivalent of doing what
--reference does during the clone)?

yes, just make sure the objects/info/alternates file points to the
location of that cloned repo's object directory; for example:

  $ echo /path/to/cloned/repo/.git/objects > .git/objects/info/alternates

-- 
Cheers,
Ray Chuan

On Sat, Feb 27, 2010 at 10:37:25AM +0800, Tay Ray Chuan wrote:

yes, just make sure the objects/info/alternates file points to the
location of that cloned repo's object directory; for example:

  $ echo /path/to/cloned/repo/.git/objects > .git/objects/info/alternates

You will probably want to then get rid of anything in the child that is
now available in the alternates repository.

I would have thought "git repack -adl" works, but I think there is
something a little funny in the logic. It reports "nothing new to pack",
but does not delete the loose objects. But packing first then worked:

  $ git clone large-parent child
  $ echo $PWD/large-parent/.git/objects >child/.git/objects/info/alternates
  $ cd child

  $ du -sh .git/objects
  51M     .git/objects

  $ git repack -adl && du -sh .git/objects
  Nothing new to pack.
  51M     .git/objects

  $ git repack -ad && du -sh .git/objects
  Counting objects: 3, done.
  Delta compression using up to 2 threads.
  Compressing objects: 100% (2/2), done.
  Writing objects: 100% (3/3), done.
  Total 3 (delta 0), reused 0 (delta 0)
  51M     .git/objects

  $ git repack -adl && du -sh .git/objects
  Nothing new to pack.
  20K     .git/objects

-Peff

Jeff King <peff <at> peff.net> writes:

On Sat, Feb 27, 2010 at 10:37:25AM +0800, Tay Ray Chuan wrote:

quoted

yes, just make sure the objects/info/alternates file points to the
location of that cloned repo's object directory; for example:

  $ echo /path/to/cloned/repo/.git/objects > .git/objects/info/alternates

You will probably want to then get rid of anything in the child that is
now available in the alternates repository.

I would have thought "git repack -adl" works, but I think there is
something a little funny in the logic. It reports "nothing new to pack",
but does not delete the loose objects. But packing first then worked:

  $ git clone large-parent child
  $ echo $PWD/large-parent/.git/objects >child/.git/objects/info/alternates
  $ cd child

  $ du -sh .git/objects
  51M     .git/objects

  $ git repack -adl && du -sh .git/objects
  Nothing new to pack.
  51M     .git/objects

  $ git repack -ad && du -sh .git/objects
  Counting objects: 3, done.
  Delta compression using up to 2 threads.
  Compressing objects: 100% (2/2), done.
  Writing objects: 100% (3/3), done.
  Total 3 (delta 0), reused 0 (delta 0)
  51M     .git/objects

  $ git repack -adl && du -sh .git/objects
  Nothing new to pack.
  20K     .git/objects

-Peff

Excellent, this is exactly what I need. Thanks very much Tay
 and Jeff.

I now have a plan to write a script to attach and
detach repositories to and from local mirrors on demand:

attach = 
    echo "/path/to/mirror" > .git/objects/info/alternates && 
    git repack -adl && 
    git repack -ad && 
    git repack -adl

detach = 
    git repack -a && 
    rm .git/objects/info/alternates


Cheers,
Steve

On Sat, Feb 27, 2010 at 11:43:55AM +0000, Steve Folly wrote:

I now have a plan to write a script to attach and
detach repositories to and from local mirrors on demand:

I think they should work, but:

attach = 
    echo "/path/to/mirror" > .git/objects/info/alternates && 
    git repack -adl && 
    git repack -ad && 
    git repack -adl

I don't think the first repack is doing anything (I showed it in my
example only to show that it was not actually working).

-Peff

On Sat, Feb 27, 2010 at 3:30 PM, Jeff King [off-list ref] wrote:

On Sat, Feb 27, 2010 at 11:43:55AM +0000, Steve Folly wrote:

quoted

attach =
    echo "/path/to/mirror" > .git/objects/info/alternates &&
    git repack -adl &&
    git repack -ad &&
    git repack -adl

I don't think the first repack is doing anything (I showed it in my
example only to show that it was not actually working).

That's a bug, isn't it? Has anyone taken a look into it?

-- 
Felipe Contreras

On Sun, May 16, 2010 at 04:55:21PM +0300, Felipe Contreras wrote:

On Sat, Feb 27, 2010 at 3:30 PM, Jeff King [off-list ref] wrote:

quoted

On Sat, Feb 27, 2010 at 11:43:55AM +0000, Steve Folly wrote:

quoted

attach =
    echo "/path/to/mirror" > .git/objects/info/alternates &&
    git repack -adl &&
    git repack -ad &&
    git repack -adl

I don't think the first repack is doing anything (I showed it in my
example only to show that it was not actually working).

That's a bug, isn't it? Has anyone taken a look into it?

Yes, it's a bug. I don't think anybody is looking at it. I started to
write a length explanation, but the more I thought about it, the more I
am not actually sure what is going on. So please, if you are interested,
take a look and see if you can come up with a patch.

-Peff