Analyzing a corrupted index file

Hello all,

I have a corrupted git index file, and am trying to read it by hand, to understand what's wrong with it. Are there any tools that'll let me parse the on-disk, binary version of the index file, to unpack it into a human-readable data structure? I found the spec for the index binary format, but reading it in that way is beyond my abilities.

For context, I'm writing a git tool, and my code is causing the index file to be screwed up in some unknown way. When it's in that state, git (v2.43) becomes inconsistent with itself:
- In the workdir, the file contains A
- According to `git show :file`, the file in the index contains B
- But `git diff` reports no changes!
The inconsistency goes away with a simple `git reset`, but can then be easily reproduced by re-executing my tool.

Thank you, Nathan