From: Avery Pennarun <apenwarr@gmail.com>
Date: Fri, 21 Aug 2009 22:39:49 GMT
Subject: Re: Raw commands to add object to existing tree
Message-ID: <32541b130908211539ke64bd2bif0aa7cff6bc6ae8f@mail.gmail.com>
In-Reply-To: <ef72456d0908211531m5e261805p2f67d3a8a16a0b5@mail.gmail.com>

On Fri, Aug 21, 2009 at 10:31 PM, D Sundstrom<sunds@peapod.net> wrote:
> Both the community git manual:
> http://book.git-scm.com/7_raw_git.html
>
> and Pro Git book:
> http://progit.org/book/ch9-2.html
>
> walk you though low level details of creating objects and trees in git, and
> then committing these new trees.
>
> However, they do not show you how to add and commit into existing trees.

Naturally, you can't change an "existing" tree, because any given tree
(identified by its sha-1 hash) can never change.  You presumably want
to create a *new* tree and commit that.

The easiest way I know to do this is to create a new indexfile, fill
it with what you want, and create the tree for that.

(Warning: untested code follows)

export GIT_INDEX_FILE=/tmp/my-temp-index
git read-tree PREVIOUS_COMMIT_OR_TREE_ID
hash=$(git hash-object NEW_FILE)
git update-index --cacheinfo "0644 $hash path/of/file/in/tree"
commitid=$(echo COMMIT MESSAGE | git commit-tree $(git write-tree))
git update-ref refs/heads/BRANCHNAME $commitid PREVIOUS_COMMIT_OR_TREE_ID

Have fun,

Avery