[PATCH 0/6] hash: introduce unsafe_hash_algo(), drop unsafe_ variants

(This series is based on my 'tb/sha1-unsafe-helper', which I sent to the list here[1].)

This series implements an idea discussed in [2] which suggests that we introduce a way to access a wrapped version of a 'struct git_hash_algo' which represents the unsafe variant of that algorithm, rather than having individual unsafe_ functions (like unsafe_init_fn() versus init_fn(), etc.).

This approach is relatively straightforward to implement, and removes a significant deficiency in the original implementation of unsafe/non-cryptographic hash functions by making it impossible to switch between safe- and unsafe variants of hash functions. It also cleans up the sha1-unsafe test helper's implementation by removing a large number of "if (unsafe)"-style conditionals.

The series is laid out as follows:

  * The first two patches prepare the hashfile API for the upcoming
    change:

      csum-file: store the hash algorithm as a struct field
      csum-file.c: extract algop from hashfile_checksum_valid()

  * The next patch implements the new 'unsafe_hash_algo()' function at
    the heart of this series' approach:

      hash.h: introduce `unsafe_hash_algo()`

  * The next two patches convert existing callers to use the new
    'unsafe_hash_algo()' function, instead of switching between safe and
    unsafe_ variants of individual functions:

      csum-file.c: use unsafe_hash_algo()
      t/helper/test-hash.c: use unsafe_hash_algo()

  * The final patch drops the unsafe_ function variants following all
    callers being converted to use the new pattern:

      hash.h: drop unsafe_ function variants

Thanks in advance for your review!

[1]: https://lore.kernel.org/git/cover.1730833506.git.me@ttaylorr.com/ [2]: https://lore.kernel.org/git/20241107013915.GA961214@coredump.intra.peff.net/

Taylor Blau (6):
  csum-file: store the hash algorithm as a struct field
  csum-file.c: extract algop from hashfile_checksum_valid()
  hash.h: introduce `unsafe_hash_algo()`
  csum-file.c: use unsafe_hash_algo()
  t/helper/test-hash.c: use unsafe_hash_algo()
  hash.h: drop unsafe_ function variants

 csum-file.c          | 33 ++++++++++++++++++---------------
 csum-file.h          |  1 +
 hash.h               | 20 +++++---------------
 object-file.c        | 41 ++++++++++++++++++++++++++---------------
 t/helper/test-hash.c | 17 +++++------------
 5 files changed, 55 insertions(+), 57 deletions(-)

base-commit: d8c1fc78b57e02a140b5c363caaa14c2dc2bb274