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Exception suggestion: raise when making a Commit with non-commit binsha #2254
Description
Activity
- added a commit that references this issue on Sep 28, 2026
I have a partial fix for it, which is in the realm of what can be done without affecting performance noticably.
CodexThe proposed fix catches the type mismatch before parsing: accessing Commit(repo, tag.binsha).tree for an annotated tag now raises a clear ValueError identifying the SHA, actual type, and expected type, instead of the unrelated IndexError.
The audit also improved related paths:
- The same validation covers blobs, trees, tags, and raw tree traversals used by index operations.
- IndexFile.new() now preserves binary SHA inputs instead of converting them into Python string representations.
- Submodule diffs now represent their commit IDs without incorrectly treating them as blobs.
Commit(repo, tag.binsha) itself still succeeds. Constructors remain lazy because checking there would require a database lookup for every object created and interfere with representing placeholders or objects unavailable locally. Validation happens when metadata or data is requested.
Consider the following code snippet:
If GitPython is a repo in the CWD, then upon running the above code, you will see a traceback like so:
Traceback (most recent call last): File "my_python_file.py", line 5, in <module> index_file = git.IndexFile.new(repo, commit.tree) File "/usr/lib/python3.14/site-packages/git/index/base.py", line 330, in new base_entries = aggressive_tree_merge(repo.odb, tree_sha_bytes) File "/usr/lib/python3.14/site-packages/git/index/fun.py", line 505, in aggressive_tree_merge for entry in traverse_tree_recursive(odb, tree_shas[-1], ""): ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.14/site-packages/git/objects/fun.py", line 271, in traverse_tree_recursive data = tree_entries_from_data(odb.stream(tree_sha).read()) File "/usr/lib/python3.14/site-packages/git/objects/fun.py", line 111, in tree_entries_from_data while data[i] != 0: ~~~~^^^ IndexError: index out of rangeThis throws an out-of-bounds array index exception when trying to parse the tag's database stream as a tree, which should fail. However, the real user error occurred when trying to make a Commit object from a tag object's binsha: commit = git.Commit(repo, tag.binsha). The Commit constructor should raise an Exception with a message to this effect. For example, "Given sha value does not refer to a commit`.