Skip tags that point to blob objects instead of commits

[humitos]

Maybe this is not the best solution ever since we may be skipping other cases also since I'm catching the ValueError exception (too general) but initially we want to skip them, log and continue building.

Closes #4440

[davidfischer]

This is fine but you can get the full traceback with exc_info=True if you want.

[safwanrahman]

I think it should be rewritten as following

repo = git.Repo(self.working_dir)
versions = []
for tag in repo.tags:
     tag_obj = tag.tag
     commit_obj = tag_obj.object
     tag_name = tag_obj.tag
     versions.append(VCSVersion(self, commit_obj.hexsha, tag_name))

tag.TagObject has the object option which actually points to the commit. It will not raise valueError like the Refs.tag.commit

[humitos]

Yeah, I found that when I was researching about this but... is this something useful for Read the Docs? I mean, that blob object where the tag is pointing is something we can build?

I considered that and I thought that it will be useless/tricky/not valid for Read the Docs to consider that as a tag (version) that we want to build.

What do you think?

[safwanrahman]

I think as its a feature of git, we should support it. Many projects may use this feature and tag without commit is also in linux kernel. So from RTD point of view, its a tag and we should not consider whethere the tag is pointed to any commit or blob!

[davidfischer]

A tag can point to a blob, a tree, or even another tag. However, the vast majority of tags across all repos point to commits. A repository that has a non-commit tag is using it for a special purpose (say, it points to a blob of the public key used by the project). With the admittedly limited examples of non-commit tags I've seen none of them could be built as documentation by Read the Docs.

I think it's safe to completely ignore non-commit tags. I would love to see examples of non-commit tags that would somehow be sensible to Read the Docs.

[davidfischer]

I think it's safe to completely ignore non-commit tags.

At least until somebody requests it. The fact that nobody has requested it and that non-commit tags caused a repo to fail building on Read the Docs is definitely something to consider as well.

[safwanrahman]

I believe if we can support the non commit tags, we should support it. We should not wait till someone open a issue with "My build is not working because my tag does not belong to a commit".

In the solution I provided, we can still support non commit tag as well as commit tag. So why do we exclude the non commit tag?

[davidfischer]

It won't work. It will just fail later. When you attempt to checkout a non-commit tag in git like we do when we attempt to build documentation, you'll get the error:

fatal: reference is not a tree: TAG-NAME

[safwanrahman]

Oh! I understand! Than I think its better to not have them in Version! Thanks @davidfischer

[agjohnson]

Looks like this can be merged. We can return to tighten the exception handling later