Re: [PATCH v5 2/3] apply: make i-t-a entries never match worktree

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Raymond

On 08/08/2020 15:07, Raymond E. Pasco wrote:
> On Sat Aug 8, 2020 at 9:46 AM EDT, Phillip Wood wrote:
>>> By definition, an intent-to-add index entry can never match the
>>> worktree, because worktrees have no concept of intent-to-add entries.
>>> Therefore, "apply --index" should always fail on intent-to-add paths.
>>
>> I'm not sure I understand the logic for this. If I run 'git add -N
>> <path>' and <path> does not exist in the worktree what's the reason to
>> stop a patch that creates <path> from applying?
> 
> "apply --index" requires the index and worktree to match, and applies
> the same path to both to get the same result in both. I brainstormed the
> logic a few emails upthread, and that's what's consistent with
> everything else.

I had a quick scan of the earlier email and found

 > The index and the filesystem are both able to represent "no file"
 > and "a file exists" states, but the index has an additional
 > state (i-t-a) with no direct representation in the
 > worktree. By (correctly) emitting "new file" patches when
 > comparing a file to an i-t-a index entry, we are setting down the
 > rule that a "new file" patch is not merely the diff between "no
 > file" and "a file exists", but also the diff between i-t-a and "a
 > file exists".
 >
 > Similarly, "deleted file" patches are the diff between "a file
 > exists" and "no file exists", but they are also the diff between
 > i-t-a and "no file exists" - if you add -N a file and then delete
 > it from the worktree, "deleted file" is what git diff (correctly)
 > shows. As a consequence of these rules, "new file" and "deleted
 > file" diffs are now the only diffs that validly apply to an i-t-a
 > entry. So apply needs to handle them (in "--cached" mode,
 > anyway).

If I've understood correctly an i-t-a entry in the index combined with 
nothing in the worktree is a deletion and that is why we don't want 
--index to succeed when applying a creation patch? If so an expanded 
explanation in the commit message to this patch would help rather than 
just saying 'by definition'. I'm still a bit confused as we don't count 
it as a deletion when using --cached or applying to the worktree.

>> I was relieved to see from the next patch that this does not affect
>> --cached even though the documentation says it implies --index. It might
>> be worth mentioning that in the commit message. Also it would be easier
>> to follow if the tests were in the same patch (this is what we usually
>> do).
> 
> --cached doesn't really imply --index - the docs are wrong and should be
> changed. If anything, --index is closer to implying --cached - but
> really, [no flags], --cached, and --index are three different modes with
> different behavior. (Just removing "this implies --index" would be
> sufficient to make the docs correct.)
> 
>> How this does it affect --check? `git add -p` uses --check to verify
>> that hunks that the user has edited still apply. It does not let the
>> user edit the hunk for a newly added file at the moment but that is
>> something I'm thinking of adding.
> 
> --check goes through all the same code, 

The same code as --cached or --index? (I assume it's the former but 
wanted to be sure)

Thanks

Phillip

>it just doesn't actually touch
> anything in the index or worktree. Splittable/editable new file patches
> are a logical related feature, IMO. (This is just to squash an error
> that shouldn't happen.)
>