From: Junio C Hamano <junkio@cox.net>
Date: Mon, 08 Aug 2005 20:47:09 GMT
Subject: Re: "git revert" (Re: pci_update_resource() getting called on sparc64)
Message-ID: <7vd5oo40mq.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.58.0508081257190.3258@g5.osdl.org>

Linus Torvalds <torvalds@osdl.org> writes:

>> It may not have the nicest error messages: if you try to revert a merge
>> (which won't have a diff), git-apply will say something like
>> 
>> 	fatal: No changes
>> 
>> which isn't exactly being helpful. And the revert message could be made 
>> more interesting (like putting the first line of the description of what 
>> we reverted into the message instead of just the revision number).

> Comments?
>
> 		Linus

I like the general idea, and if we had a commit pretty format
"oneline", then something like this would make it look nicer.

Totally untested.  I acquired your habit of coding in my e-mail
client ;-).

        #!/bin/sh
        . git-sh-setup-script || die "Not a git archive"

        rev=$(git-rev-parse --verify --revs-only "$@") &&
        commit=$(git-rev-parse --verify --revs-only "$commit^0") || exit
        if git-diff-tree -R -p $commit | git-apply --index &&
           msg=$(git-rev-list --pretty=oneline --max-count=1 $commit)
        then
                {
                        echo "Revert $msg"
                        echo
                        echo "This reverts $commit commit."
                        test "$rev" = "$commit" ||
                        echo "(original 'git revert' arguments: $@)"
                } | git commit
        else
                # Now why did it fail?
                parents=`git-cat-file commit "$commit" 2>/dev/null |
                        sed -ne '/^$/q;/^parent /p' |
                        wc -l`
                case $parents in
                0) die "Cannot revert the root commit nor non commit-ish" ;;
                1) die "The patch does not apply" ;;
                *) die "Cannot revert a merge commit" ;;
                esac
        fi