Re: How to create a new commit with the content of some commit?

[Jeff King <peff@peff.net>]

On Wed, May 13, 2009 at 12:43:33AM +0800, Ping Yin wrote:

> > You can just munge the index directly, and skip the working tree
> > entirely:
> >
> >  rm .git/index
> >  git read-tree b
> >  git commit -m 'the copy of b'
> 
> In a non-conflict status, "git read-tree b" will update the index to
> full match the tree of b, so "rm .git/index" is unnecessary, right?

For some reason, I was thinking that entries in the index that were not
in "b" would remain, but that is not actually the case. So yes, I think
you can do it without removing the index (and you are better off to do
so, since the index also contains the stat cache for your worktree, so
it is more efficient).

You can also add "-u" as Junio suggested to update the working tree
during that step, which should be more efficient.

> >  echo 'copy of b' >message
> >  tree=`git rev-parse b^{tree}`
> >  commit=`git commit-tree $tree -p c <message`
> >  git update-ref c $commit
> 
> Maybe a -c option can be added to git-commit-tree?

I doubt there is much interest in that, as commit-tree is meant to be a
low-level building block, not a user tool. If you wanted to pull the
message from another commit, you could just do:

  git cat-file commit b | sed '1,/^$/d' | git commit-tree ...

-Peff