Re: [PATCH v2] doc: remove misleading documentation on pack names

[Johannes Berg <johannes@sipsolutions.net>]

On Wed, 2020-07-22 at 14:09 -0700, Junio C Hamano wrote:
> 
> Please avoid "seems to be" and spend a bit of effort digging the
> history especially when we are not in a hurry to get to the definite
> answer.

I did ... but between all the file renames and moves, and not
understanding the code very well, I didn't really understand what was
going on.

Ok, so maybe "seems to be" was a bit of a cop-out because I do
understand that's what git does *now* (having just replicated it in
bup), but I have no idea how it got there.

> We can go "less explicit", or be a bit more informative by
> saying that it is the trailer hash that is standard practice shared
> across our binary files like the index and the packfile.
> 
> I think this is 1190a1ac (pack-objects: name pack files after
> trailer hash, 2013-12-05).

Indeed, that makes sense. Somehow I didn't come across this commit, but
perhaps that's because I was looking too much at index-pack.c (and its
various renames).

>   It forgot to update the comment before
> write_idx_file() function when it did this change:
> 
>  /*
>   * On entry *sha1 contains the pack content SHA1 hash, on exit it is
>   * the SHA1 hash of sorted object names. The objects array passed in
>   * will be sorted by SHA1 on exit.
>   */
>  const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
>  			   int nr_objects, const struct pack_idx_option *opts,
> -			   unsigned char *sha1)
> +			   const unsigned char *sha1)
>  {
> 
> Obviously, after it turned *sha1 into 'const', it no longer is
> possible for it to have anything different from what was passed in
> upon exit.

Indeed :-)

> > +Once the index has been created, the hash that goes into the name of
> > +the pack/idx file is printed to stdout. If --stdin was also used then
> > +this is prefixed by either "pack\t", or "keep\t" if a new .keep file
> > +was successfully created. This is useful to remove a .keep file used
> > +as a lock to prevent the race with 'git repack' mentioned above.
> 
> The change is good---I made sure that among these filve lines, what
> changed was only the first one and half lines.  I however would have
> preferred not to see the line rewrapping.

Ok, fair - the text all seemed wrapped "nicely" so I preserved that
rather than have one line significantly shorter than the others, but if
you prefer that it's fine by me.

Really all I was trying to do is be a *little* more helpful than just
point out "the documentation is wrong"...

johannes