Merge branch 'ds/chunked-file-api'

Merge branch 'ds/chunked-file-api'

The common code to deal with "chunked file format" that is shared
by the multi-pack-index and commit-graph files have been factored
out, to help codepaths for both filetypes to become more robust.

* ds/chunked-file-api:
  commit-graph.c: display correct number of chunks when writing
  chunk-format: add technical docs
  chunk-format: restore duplicate chunk checks
  midx: use 64-bit multiplication for chunk sizes
  midx: use chunk-format read API
  commit-graph: use chunk-format read API
  chunk-format: create read chunk API
  midx: use chunk-format API in write_midx_internal()
  midx: drop chunk progress during write
  midx: return success/failure in chunk write methods
  midx: add num_large_offsets to write_midx_context
  midx: add pack_perm to write_midx_context
  midx: add entries to write_midx_context
  midx: use context in write_midx_pack_names()
  midx: rename pack_info to write_midx_context
  commit-graph: use chunk-format write API
  chunk-format: create chunk format write API
  commit-graph: anonymize data in chunk_write_fn