Bug summary

The Reference.TagReference.tag() function in the module git/refs/tag.py in Gitpython 2.1.0 (and potentially other versions after 2.0.8) does not properly handle lightweight tags that point to blobs or trees.

Below I will demonstrate how to create a tag pointing to a blob or tree. Next I will demonstrate how to trigger the bug in gitpython. Finally, I will show an example popular git repo that contains a tag pointing to a tree.

I do not have a suggestion for what the correct behavior of Reference.TagReference.tag() should be, but I do not think that it should trigger an exception when the tag points to a blob or tree.

Sample script to create a repo with a tag pointing to a blob

git init foocd fooecho foo> bar.txtgit add bar.txtgit commit -m bazgit tag quux`git hash-object bar.txt`PAGER=cat git show quuxcd ..

Python script to trigger the bug (using the above repo)

# pip install gitpython==2.1.0importgittag_name="quux"repo_name="foo"repo_obj=git.Repo(repo_name)tag_obj=repo_obj.tags[0]assertstr(tag_obj)==tag_nameiftag_obj.commit.type=='commit':print("Is a commit")else:print("Not a commit")

Traceback from test script

Traceback (most recent call last):  File "delme.py", line 10, in <module>    if tag_obj.commit.type == 'commit':  File "/usr/lib/python2.7/site-packages/git/refs/tag.py", line 33, in commit    raise ValueError("Tag %s points to a Blob or Tree - have never seen that before" % self)ValueError: Tag quux points to a Blob or Tree - have never seen that before

Example from the wild: linux

Here I will show an example of a popular git repo that includes a tag (v2.6.11) pointing to a blob or tree. Note that Linus Torvalds, the original author of git, probably created this tag, based on the fact that he authored the successively-named tag (v2.6.12-rc2). v2.6.11 does not contain metadata.

Running these commands:

git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-stablecd linux-stablegit show v2.6.11

Produces this output:

tag v2.6.11-treeThis is the 2.6.11 tree object.NOTE! There's no commit for this, since it happened before I started with git.Eventually we'll import some sort of history, and that should tie this treeobject up to a real commit. In the meantime, this acts as an anchor point fordoing diffs etc under git.-----BEGIN PGP SIGNATURE-----Version: GnuPG v1.2.4 (GNU/Linux)iD8DBQBCeV/eF3YsRnbiHLsRAl+SAKCVp8lVXwpUhMEvy8N5jVBd16UCmACeOtP6KLMHist5yj0sw1E4hDTyQa0==/bIK-----END PGP SIGNATURE-----tree v2.6.11COPYINGCREDITSDocumentation/MAINTAINERSMakefileREADMEREPORTING-BUGSarch/crypto/drivers/fs/include/init/ipc/kernel/lib/mm/net/scripts/security/sound/usr/