Re: [PATCH v3 1/4] replace: add --graft option

Jeff King [off-list ref] writes:

I think it would make sense to actually take this one step further,
though, and move commit->buffer into the slab, as well. That has two
advantages:

  1. It further decreases the size of "struct commit" for callers who do
     not use save_commit_buffer.

  2. It ensures that no new callers crop up who set "commit->buffer" but
     to not save the size in the slab (you can see in the patch below
     that I had to modify builtin/blame.c, which (ab)uses
     commit->buffer).

It would be more disruptive to existing callers, but I think the end
result would be pretty clean. The API would be something like:

  /* attach buffer to commit */
  set_commit_buffer(struct commit *, void *buf, unsigned long size);

  /* get buffer, either from slab cache or by calling read_sha1_file */
  void *get_commit_buffer(struct commit *, unsigned long *size);

  /* free() an allocated buffer from above, noop for cached buffer */
  void unused_commit_buffer(struct commit *, void *buf);

  /* drop saved commit buffer to free memory */
  void free_commit_buffer(struct commit *);

The "get" function would serve the existing callers in pretty.c, as well
as the one I'm adding elsewhere in show_signature. And it should work as
a drop-in read_sha1_file/free replacement for you here.

This solution has the kind of niceness to make everybody (certainly
including me) who has been involved in the code path should say "why
didn't I think of that!" ;-)