[PATCH] contrib/subtree bugfix: Can't `add` annotated tag

[PATCH] contrib/subtree bugfix: Can't `add` annotated tag

[James Denholm]

cmd_add_commit() is passed FETCH_HEAD by cmd_add_repository, which is
then rev-parsed into an object ID. However, if the user is fetching a
tag rather than a branch HEAD, such as by executing:

$ git subtree add -P oldGit https://github.com/git/git.git tags/v1.8.0

The object ID is a tag and is never peeled, and the git commit-tree call
(line 561) slaps us in the face because it doesn't handle tag IDs.

Because peeling a committish ID doesn't do anything if it's already a
commit, fix by peeling[1] the object ID before assigning it to $rev, as
per the patch.

[*1*]: Via peel_committish(), from git:git-sh-setup.sh

Reported-by: Kevin Cagle <kcagle@micron.com>
Diagnosed-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: James Denholm <nod.helm@gmail.com>
---
NB: This bug doesn't surface when using --squash, as $rev is reassigned
to the squash commit via new_squash_commit before git commit-tree sees
it (though for simplicity, new_squash_commit now also sees the peeled
ID).

Also doesn't surface when using "git subtree merge", as git merge can
handle tag objects.

On a side note, if merging a tag without --squash, git merge recognises
that it's a tag and adds a note to the merge commit body. It may be
worth mimicking this when using "subtree merge --squash" or
"subtree add".

 contrib/subtree/git-subtree.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index dc59a91..9453dae 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -538,7 +538,7 @@ cmd_add_commit()
 {
 	revs=$(git rev-parse $default --revs-only "$@") || exit $?
 	set -- $revs
-	rev="$1"
+	rev=$(peel_committish "$1")
 	
 	debug "Adding $dir as '$rev'..."
 	git read-tree --prefix="$dir" $rev || exit $?
-- 
1.9.2

Re: [PATCH] contrib/subtree bugfix: Can't `add` annotated tag

[Junio C Hamano]

James Denholm <nod.helm@gmail.com> writes:

> cmd_add_commit() is passed FETCH_HEAD by cmd_add_repository, which is
> then rev-parsed into an object ID. However, if the user is fetching a
> tag rather than a branch HEAD, such as by executing:
>
> $ git subtree add -P oldGit https://github.com/git/git.git tags/v1.8.0
>
> The object ID is a tag and is never peeled, and the git commit-tree call
> (line 561) slaps us in the face because it doesn't handle tag IDs.

The "rev" (not "revs") seems to be used by more things than the
final commit-tree state.  Are we losing some useful information by
peeling it too early like this patch does?  The reason why we
stopped peeling when writing FETCH_HEAD was because we wanted to
record the fact that we merged a tag (and use the GPG signature if
found in it) when constructing the log message for the merge, and
peeling the tag too early and recording the commit in FETCH_HEAD
would make it impossible to do, and I am wondering if this change is
making the same kind of mistake here.

I see that add_msg does not use anything useful from latest_new, so
with the current state of the code, it does not make that much
difference (except that it says "from commit '$latest_new'", and by
peeling, the fact that the user wanted to use a tag is lost from the
result).

> On a side note, if merging a tag without --squash, git merge recognises
> that it's a tag and adds a note to the merge commit body. It may be
> worth mimicking this when using "subtree merge --squash" or
> "subtree add".

Yes, and this change makes such a change harder to implement on top,
I suspect.

Would it be sufficient to do

	git commit-tree $tree $headp -p "$rev^0"

in that "not squashing" codepath instead?

>  contrib/subtree/git-subtree.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
> index dc59a91..9453dae 100755
> --- a/contrib/subtree/git-subtree.sh
> +++ b/contrib/subtree/git-subtree.sh
> @@ -538,7 +538,7 @@ cmd_add_commit()
>  {
>  	revs=$(git rev-parse $default --revs-only "$@") || exit $?
>  	set -- $revs
> -	rev="$1"
> +	rev=$(peel_committish "$1")
>  	
>  	debug "Adding $dir as '$rev'..."
>  	git read-tree --prefix="$dir" $rev || exit $?

Re: [PATCH] contrib/subtree bugfix: Can't `add` annotated tag

[James Denholm]

Junio C Hamano <gitster@pobox.com> wrote:
> The "rev" (not "revs") seems to be used by more things than the
> final commit-tree state.  Are we losing some useful information by
> peeling it too early like this patch does? (...)

You're not wrong, actually, peeling at the last minute (or at least
later) would be a better choice. I'd suggest that we aren't losing
currently-useful information (as it'd be rare-if-ever that a user would
look at a hash in their commit logs and think "Oh, that's that tag!"),
but certainly with future development in mind it's more ideal.

> I see that add_msg does not use anything useful from latest_new, so
> with the current state of the code, it does not make that much
> difference (except that it says "from commit '$latest_new'", and by
> peeling, the fact that the user wanted to use a tag is lost from the
> result).

Yeah, that might be a worthy thing to porcelain-up in the future with
logging the tag name rather than, or in addition to, the hash, as well
as a similar change in add_squashed_msg.

> Would it be sufficient to do
>
>         git commit-tree $tree $headp -p "$rev^0"
>
> in that "not squashing" codepath instead?

On line 561, sure. Do you want me to do a re-roll?

Re: [PATCH] contrib/subtree bugfix: Can't `add` annotated tag

[James Denholm]

On Fri, May 09, 2014 at 05:36:15PM +1000, James Denholm wrote:
> Junio C Hamano <gitster@pobox.com> wrote:
> > Would it be sufficient to do
> >
> >         git commit-tree $tree $headp -p "$rev^0"
> >
> > in that "not squashing" codepath instead?
> 
> On line 561, sure. Do you want me to do a re-roll?

Sorry to bump, but do you want a reroll on this?

---
Regards,
James Denholm.