# tag referring to a commit but not directly? 3 messages from 2005-07-09 to 2005-07-11. Participants: Junio C Hamano, Jon Seymour. Thread: https://gitlist.dev/t/1185 ## Junio C Hamano, 2005-07-09 10:00 Subject: tag referring to a commit but not directly? Message-ID: <7v7jg0wb77.fsf@assigned-by-dhcp.cox.net> URL: https://gitlist.dev/e/7v7jg0wb77.fsf%40assigned-by-dhcp.cox.net ``` I was playing with a tag that refers to another tag which refers to a commit, and found out that some things did not work as I expected. Is it a PEBCAK on my part to expect tag-to-tag-to-commit to behave the same way as a bare commit (or a tag to commit), or is this just a bug? I think the following two would fix what I found, but I am not sure if I am using the "struct object" and friends the way they are expected to be used. I am uncertain about what the expected behaviour should be either for that matter; I admit that tags are new to me. --- *** To find whom to ask about the thing I am butchering, I *** used the following pickaxe: git-rev-list linus | git-diff-tree --stdin -v -s \ -S' if (obj->type == tag_type) obj = ((struct tag *)obj)->tagged;' git-rev-list linus | git-diff-tree --stdin -v -s \ -S' /* * Tag object? Look what it points to.. */ if (object->type == tag_type) {' ------------ cd /opt/packrat/playpen/public/in-place/git/git.junio/ jit-diff 0:5 # - master: format-patch: fix skipping of blank-lines (take 2) # + 5: tag deref until we get non tag diff --git a/commit.c b/commit.c --- a/commit.c +++ b/commit.c @@ -52,8 +52,9 @@ struct commit *lookup_commit_reference(c if (!obj) return NULL; - if (obj->type == tag_type) - obj = ((struct tag *)obj)->tagged; + while (obj->type == tag_type) + obj = parse_object(((struct tag *)obj)->tagged->sha1); + return check_commit(obj, sha1); } diff --git a/rev-list.c b/rev-list.c --- a/rev-list.c +++ b/rev-list.c @@ -354,12 +354,12 @@ static struct commit *get_commit_referen /* * Tag object? Look what it points to.. */ - if (object->type == tag_type) { + while (object->type == tag_type) { struct tag *tag = (struct tag *) object; object->flags |= flags; if (tag_objects && !(object->flags & UNINTERESTING)) add_pending_object(object, tag->tag); - object = tag->tagged; + object = parse_object(tag->tagged->sha1); } /* Compilation finished at Sat Jul 9 02:37:16 ``` ## Junio C Hamano, 2005-07-11 06:55 Subject: [PATCH] Dereference tag repeatedly until we get a non-tag. Message-ID: <7v8y0dx24j.fsf@assigned-by-dhcp.cox.net> URL: https://gitlist.dev/e/7v8y0dx24j.fsf%40assigned-by-dhcp.cox.net In-Reply-To: <7v7jg0wb77.fsf@assigned-by-dhcp.cox.net> ``` When we allow a tag object in place of a commit object, we only dereferenced the given tag once, which causes a tag that points at a tag that points at a commit to be rejected. Instead, dereference tag repeatedly until we get a non-tag. This patch makes change to two functions: - commit.c::lookup_commit_reference() is used by merge-base, rev-tree and rev-parse to convert user supplied SHA1 to that of a commit. - rev-list uses its own get_commit_reference() to do the same. Dereferencing tags this way helps both of these uses. Signed-off-by: Junio C Hamano --- *** Whether having a tag pointing at another tag is a separate *** issue, but I do not see a reason to forbid it. Maybe it *** is used to represent a chain of trust. commit.c | 5 +++-- rev-list.c | 4 ++-- 2 files changed, 5 insertions(+), 4 deletions(-) 0dc9377363ee73c5e3f3711d6f82e49886ce8c6a diff --git a/commit.c b/commit.c --- a/commit.c +++ b/commit.c @@ -52,8 +52,9 @@ struct commit *lookup_commit_reference(c if (!obj) return NULL; - if (obj->type == tag_type) - obj = ((struct tag *)obj)->tagged; + while (obj->type == tag_type) + obj = parse_object(((struct tag *)obj)->tagged->sha1); + return check_commit(obj, sha1); } diff --git a/rev-list.c b/rev-list.c --- a/rev-list.c +++ b/rev-list.c @@ -367,12 +367,12 @@ static struct commit *get_commit_referen /* * Tag object? Look what it points to.. */ - if (object->type == tag_type) { + while (object->type == tag_type) { struct tag *tag = (struct tag *) object; object->flags |= flags; if (tag_objects && !(object->flags & UNINTERESTING)) add_pending_object(object, tag->tag); - object = tag->tagged; + object = parse_object(tag->tagged->sha1); } /* ``` ## Jon Seymour, 2005-07-11 15:14 Subject: Re: [PATCH] Dereference tag repeatedly until we get a non-tag. Message-ID: <2cfc40320507110814256bef25@mail.gmail.com> URL: https://gitlist.dev/e/2cfc40320507110814256bef25%40mail.gmail.com In-Reply-To: <7v8y0dx24j.fsf@assigned-by-dhcp.cox.net> ``` This seems reasonable to me. I have thought this would be useful on several occasions and haven't yet conceived of a counterexample where it would break something. On 7/11/05, Junio C Hamano wrote: > When we allow a tag object in place of a commit object, we only > dereferenced the given tag once, which causes a tag that points > at a tag that points at a commit to be rejected. Instead, > dereference tag repeatedly until we get a non-tag. > > This patch makes change to two functions: > > - commit.c::lookup_commit_reference() is used by merge-base, > rev-tree and rev-parse to convert user supplied SHA1 to that of > a commit. > - rev-list uses its own get_commit_reference() to do the same. > > Dereferencing tags this way helps both of these uses. > > Signed-off-by: Junio C Hamano > --- > > *** Whether having a tag pointing at another tag is a separate > *** issue, but I do not see a reason to forbid it. Maybe it > *** is used to represent a chain of trust. > > commit.c | 5 +++-- > rev-list.c | 4 ++-- > 2 files changed, 5 insertions(+), 4 deletions(-) > > 0dc9377363ee73c5e3f3711d6f82e49886ce8c6a > diff --git a/commit.c b/commit.c > --- a/commit.c > +++ b/commit.c > @@ -52,8 +52,9 @@ struct commit *lookup_commit_reference(c > > if (!obj) > return NULL; > - if (obj->type == tag_type) > - obj = ((struct tag *)obj)->tagged; > + while (obj->type == tag_type) > + obj = parse_object(((struct tag *)obj)->tagged->sha1); > + > return check_commit(obj, sha1); > } > > diff --git a/rev-list.c b/rev-list.c > --- a/rev-list.c > +++ b/rev-list.c > @@ -367,12 +367,12 @@ static struct commit *get_commit_referen > /* > * Tag object? Look what it points to.. > */ > - if (object->type == tag_type) { > + while (object->type == tag_type) { > struct tag *tag = (struct tag *) object; > object->flags |= flags; > if (tag_objects && !(object->flags & UNINTERESTING)) > add_pending_object(object, tag->tag); > - object = tag->tagged; > + object = parse_object(tag->tagged->sha1); > } > > /* > > - > To unsubscribe from this list: send the line "unsubscribe git" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- homepage: http://www.zeta.org.au/~jon/ blog: http://orwelliantremors.blogspot.com/ ```