From: Michael J Gruber <git@drmicha.warpmail.net>
Date: Fri, 21 Dec 2012 12:47:52 GMT
Subject: Re: [BUG] Cannot push some grafted branches
Message-ID: <50D45A78.3020104@drmicha.warpmail.net>
In-Reply-To: <7vvcbx956f.fsf@alter.siamese.dyndns.org>

While replace refs are much more general than grafts, it seems the two
main uses are:

- grafts (change the recorded parents for a commit)
- svn cleanup (convert tagging commits into tag objects)

The latter one being quite a special case already.

The script below has helped me move from grafts to replace objects.
While not being super clean, something like it may be fit for contrib.

I think we ought to help John Doe get along with parents, while we can
safely leave most more advanced operations to people who know how to
edit a raw object file. Putting that facility into "git-commit" seems to
be too encouraging, though - people would use replace when they should
use amend or rebase-i. I'd prefer a special git-replace mode (be it
"--graft" or "--graft-commit") which does just what my script does. We
could add things like "--commit-tag" later, a full blown
"object-factory" seems like overkill.

Michael

--->%---

#!/bin/sh

die () {
	echo "$@"
	rm -f "$commitfile"
 	exit 1
}

warn () {
	echo "$@"
}

test $# -gt 0 || die "Usage: $0 <commit> [<parent>]*"

for commit
do
	git rev-parse --verify -q "$commit" >/dev/null || die "Cannot parse
$commit."
	test x$(git cat-file -t $commit) == "xcommit" || die "$commit is no
commit."
done

commit="$1"
shift

commitfile=$(mktemp)

git cat-file commit "$commit" | while read a b
do
	if test "$a" != "parent"
	then
		echo $a $b
	fi
	if test "$a" == "tree"
	then
		for parent
		do
			echo "parent $(git rev-parse $parent)"
		done
	fi
done >$commitfile
hash=$(git hash-object -t commit -w "$commitfile") || die "Cannot create
commit object."
git replace "$commit" $hash
rm -f $commitfile