Add zlib compression feature

[harshithsaiv]

This PR adds support for Zlib(level) gated by the optional zlib Cargo feature.

Changes

• CompressionType

  • New variant: Zlib(u8).
  • Updated Encode/Decode:
    • Levels are clamped to 0..=9 on encode/decode to match flate2 expectations.

• Block I/O

  • Zlib branches added in write_into, from_reader, and from_file.
  • Compression via flate2::write::ZlibEncoder.
  • Decompression via flate2::read::ZlibDecoder.

• Blob path

  • blob_tree/compression.rs: MyCompressor added support for zlib
  • blob_tree/mod.rs: BlobTree::open() wires CompressionType::{None, Lz4, Zlib(_)} .

• Cargo.toml

  • Add optional dependency: flate2 with zlib-rs backend (default-features = false).
  • Introduce zlib feature that enables the dependency.

• No breaking changes when i ran cargo build --features zlib and cargo test --features zlib

One open point: I clamped levels ≥10 to 9 during encode. Would you prefer rejecting invalid levels instead?

[harshithsaiv]

Hi @marvin-j97 ,
Is there anything else that I should work on for this issue ? , I see that the build is failing because of files that are going to be removed as you mentioned.

[marvin-j97]

Hi @marvin-j97 , Is there anything else that I should work on for this issue ? , I see that the build is failing because of files that are going to be removed as you mentioned.

See the last remaining comment about the InvalidCompression variant

[harshithsaiv]

Hi @marvin-j97 Marvin,
I’m having trouble viewing your latest comment in the PR GitHub isn’t showing it to me. Could you please repost or clarify your feedback so I can address it? Thank you!

[marvin-j97]

Oops the review was not sent

[marvin-j97]

Just rustfmt missing I think

[marvin-j97]

I deleted the 3.0.0 branch, so this needs to rebased on main now