Re: Git conflict VC state detection

[Óscar Fuentes]

Dmitry Gutov <address@hidden> writes:

> On 10.11.2013 22:30, Óscar Fuentes wrote:
>> I've revised the initial commit implementing conflict state detection on
>> my private branch and the problem with it was that it didn't detect
>> edited state on a staged file, i.e. a file containing staged (but
>> uncommitted) changes would show as up to date.
>>
>> So I pursued a more precise method. The problem is that the git commands
>> that tells you that a file is unmerged doesn't tell that a file contains
>> changes if those are staged.
>
> Are you sure? AFAICS, 'git diff' behaves this way ('git diff' shows
> only unstages changes, 'git diff --cached' only stages ones, but 'git
> diff HEAD' will include both), but the 'git diff-index' command we're
> using already includes HEAD as the reference, and even if I do a 'git
> add' on some edited file, while 'git diff' shows me nothing, 'git
> diff-index --raw HEAD' includes the file with status M.
>
> I haven't tested it in the situation with a file being merged, though.
> Maybe that's different somehow.

With the current method in vc-git-state, this is an example where
the file keyword.cpp is unmerged:

$ git diff-index HEAD -- keyword.cpp

(-p --raw options eluded, as they just add the patch to the output,
which is useless.)

:100644 100644 12b8b5a24d99dfec20c4b5283d91b15ed1a83b4e 
0000000000000000000000000000000000000000 Mkeyword.cpp

At first, you can think that those series of zeroes mean something (the
documentation for git-diff-index says

``sha1 for "dst"; 0{40} if creation, unmerged or "look at work tree"

which is quite vague) so let's try with a plainly edited file:

$ git diff-index HEAD -- CMakeLists.txt

:100644 100644 8465aca146db66862498b9e2f2a8993e5d8dda69 
0000000000000000000000000000000000000000 MCMakeLists.txt

Hence `git diff-index' can't tell the difference among an unmerged and
an edited file.

Now let's try again but with the `--cached' option:

$ git diff-index --cached -- keyword.cpp

:100644 000000 12b8b5a24d99dfec20c4b5283d91b15ed1a83b4e 
0000000000000000000000000000000000000000 Ukeyword.cpp

There it is the `U'. But with the edited, unstaged file:

$ git diff-index --cached HEAD -- CMakeLists.txt 

<no output>

And then you need a plain "git diff-index HEAD -- CMakeLists.txt" for
knowing that the file is edited.

AFAIK there is no command that tells that a file is unmerged and also
tells that it is edited, no matter if its changes are staged or not.

>> I CC'ed Dmitry as he implemented the part that my patch touches. I'll
>> like to get the ok from him before installing the patch,
>
> I did a relatively small change there, actually, it just unwrapped all
> the code in `vc-git-registered'.

So you were wrongly "blamed" :-) Sorry about that.

> But FWIW, I don't like the idea of
> doing double the work (external process calls) to know about one more
> status, in principle.

I'm not myself happy with the solution. It all depends on how important
it is to know the `conflict' status. Maybe other features on Emacs VC
depends on it.