postprocess: support multiple transforms

[thedataking]

Support multiple transforms such that we can support different post-processing steps such as:

• comment transfer
• assert folding
• relooper cleanup
• reformatting of large tables, etc.

Some transforms might also be broken down into a sequence of simpler transforms. A concrete use case is lua which contains license headers and other matter before function definitions which we do not want to pass so the comment transfer transform.

(Replaces PR #1512 as it was automatically closed when I renamed the branch)

[Copilot]

Pull request overview

This PR refactors the c2rust postprocessing system to support multiple transforms in sequence. The main goal is to enable different post-processing steps (like comment transfer, assert folding, relooper cleanup, etc.) to be applied independently and in configurable order.

Changes:

• Introduced an abstract base class AbstractTransform to standardize transform implementations
• Renamed CommentTransfer to CommentsTransform and moved it to a new module structure
• Added factory function get_transform_by_id to instantiate transforms by name
• Updated CLI to accept comma-separated list of transforms via --transforms parameter

Reviewed changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated 16 comments.

Show a summary per file

File	Description
c2rust-postprocess/postprocess/transforms/base.py	New abstract base class defining transform interface with apply() and apply_dir() methods
c2rust-postprocess/postprocess/transforms/comments.py	Refactored comments transform with renamed classes, added validation, and AbstractTransform inheritance
c2rust-postprocess/postprocess/transforms/init.py	New factory function to instantiate transforms by ID
c2rust-postprocess/postprocess/comments/init.py	Duplicate/incomplete implementation with critical bugs that appears to be leftover from refactoring
c2rust-postprocess/postprocess/init.py	Updated main entry point to support multiple transforms and use factory pattern
c2rust-postprocess/tests/llm-cache/CommentsTransform/*/metadata.toml	Updated cache metadata to reflect "CommentsTransform" naming
c2rust-postprocess/tests/llm-cache/CommentsTransform/*/response.txt	New cached test responses for quickSort and partition functions

Comments suppressed due to low confidence (3)

c2rust-postprocess/postprocess/transforms/comments.py:69

• The docstring parameter documentation is missing the colon prefix for reST/Sphinx format. It should be :param rust_fn: and :return: instead of param: and return:.
  c2rust-postprocess/postprocess/transforms/comments.py:242
• The transfer_comments_dir method calls self.apply with a rust_source_file parameter, but the apply method signature only accepts root_rust_source_file. This mismatch will cause a TypeError at runtime. Either the apply method needs to be updated to accept rust_source_file, or this call needs to be updated to match the apply signature.
  c2rust-postprocess/postprocess/transforms/comments.py:242
• Keyword argument 'rust_source_file' is not a supported parameter name of method CommentsTransform.apply.

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