Extended splitting for "git add --interactive"

Extended splitting for "git add --interactive"

[Ulrich Windl]

Hi!

This is for git-1.7.12 (an older version from the SLES11 SP3 SDK). If the issue is solved meanwhile, I'll be happy, and I apologize for being too lazy to find out.

Currently Git cannot split a block of changes like

-AAA
-BBB
+CCC
+DDD

Into
-AAA
+CCC
and
-BBB
+DDD

So you'll have to edit it and waste me extra time (People probably use split if they know what they are doing, so maybe allow that).

Another split that is not possible is a split across an empty line, like:

+AAA
+     <empty line (in reality)>
+BBB

One could split that either into two parts with the empty lines belonging to one of AAA or BBB, or into three parts where the empty line is just another junk to accept or refuse. See comment above on why I'd like that.

Regards,
Ulrich Windl

Re: Extended splitting for "git add --interactive"

[Junio C Hamano]

"Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> writes:

> This is for git-1.7.12 (an older version from the SLES11 SP3 SDK). If
> the issue is solved meanwhile, I'll be happy, and I apologize for
> being too lazy to find out.

The answer is no ;-).

> Currently Git cannot split a block of changes like
>
> -AAA
> -BBB
> +CCC
> +DDD
>
> Into
> -AAA
> +CCC
> and
> -BBB
> +DDD

And it is unlikely to do so ever, because it is a wrong thing to do.

What makes the user happy to see above split when the user is
expecting this instead?

-AAA
and
-BBB
+CCC
+DDD

> Another split that is not possible is a split across an empty line, like:
>
> +AAA
> +     <empty line (in reality)>
> +BBB

Likewise.  An empty line is not that special.  AAA may be adding one
block of lines "if (condition) { ... }" and BBB may be another, and
it often happens that you would want to separate these into two
changes, with or without an empty line in between.

   +if (foo) {
   +  do foo thing
   +}
   +if (bar) {
   +  do bar thing
   +}
   
Having said all that, I am not opposed to a usable idea to allow the
user to specify where in a contiguous block of -*+* to break a hunk
and how.

Re: Extended splitting for "git add --interactive"

[Junio C Hamano]

Junio C Hamano <gitster@pobox.com> writes:

> "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> writes:
>
>> Another split that is not possible is a split across an empty line, like:
>>
>> +AAA
>> +     <empty line (in reality)>
>> +BBB
>
> Likewise.  An empty line is not that special.  AAA may be adding one
> block of lines "if (condition) { ... }" and BBB may be another, and
> it often happens that you would want to separate these into two
> changes, with or without an empty line in between.
>
>    +if (foo) {
>    +  do foo thing
>    +}
>    +if (bar) {
>    +  do bar thing
>    +}
>    
> Having said all that, I am not opposed to a usable idea to allow the
> user to specify where in a contiguous block of -*+* to break a hunk
> and how.

Of course, splitting at blank or at any arbitrary point that the
implementor of this new feature decides to be good is not end of the
world.  If the split at that chosen point is undesirable, the user
can join them back.  But then the feature did not help such a user
very much.  So that selection of "any arbitrary point" has to be
fairly a good heuristic, making majority of users happy, to be worth
for users to try.  If they try splitting with the heuristics and get
a good result 80% of times, 20% of time they instead may need to
join the wrong splits back, but overall it will be a win.

In an extreme case, we could have an option to split a run of zero
or more "-" lines followed by zero or more "+" lines into one line
per hunk, and let the user pick the line they want, which would
solve your original issue of turning "-A-B+C+D" into "-A+C" and
"-B+D", while allowing them to be commited with a different
splitting, e.g. "-A" and "-B+C+D".

But at that point, I suspect most people may choose to (e)dit the
patch themselves instead.  I dunno.

Antw: Re: Extended splitting for "git add --interactive"

[Ulrich Windl]

I probably forgot to mention the obvious: My enhancement request was for cases where git would reject so split a junk. I don't want to change the default split (if it finds a point to split).
So maybe call it a "2nd-level-split". Only if split refuses to split, you could avoid using "edit" to manually split.
Iknow that in gerneral such things can't be right, but you can eith reject the new junks or use "edit". I just guessed the feature could save some time on the average.

>>> Junio C Hamano <gitster@pobox.com> schrieb am 26.11.2014 um 19:57 in Nachricht
<xmqq3895rdr1.fsf@gitster.dls.corp.google.com>:
> "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> writes:
> 
>> This is for git-1.7.12 (an older version from the SLES11 SP3 SDK). If
>> the issue is solved meanwhile, I'll be happy, and I apologize for
>> being too lazy to find out.
> 
> The answer is no ;-).
> 
>> Currently Git cannot split a block of changes like
>>
>> -AAA
>> -BBB
>> +CCC
>> +DDD
>>
>> Into
>> -AAA
>> +CCC
>> and
>> -BBB
>> +DDD
> 
> And it is unlikely to do so ever, because it is a wrong thing to do.
> 
> What makes the user happy to see above split when the user is
> expecting this instead?
> 
> -AAA
> and
> -BBB
> +CCC
> +DDD
> 
>> Another split that is not possible is a split across an empty line, like:
>>
>> +AAA
>> +     <empty line (in reality)>
>> +BBB
> 
> Likewise.  An empty line is not that special.  AAA may be adding one
> block of lines "if (condition) { ... }" and BBB may be another, and
> it often happens that you would want to separate these into two
> changes, with or without an empty line in between.
> 
>    +if (foo) {
>    +  do foo thing
>    +}
>    +if (bar) {
>    +  do bar thing
>    +}
>    
> Having said all that, I am not opposed to a usable idea to allow the
> user to specify where in a contiguous block of -*+* to break a hunk
> and how.

Re: Re: Extended splitting for "git add --interactive"

[Johan Herland]

On Thu, Nov 27, 2014 at 9:55 AM, Ulrich Windl
<Ulrich.Windl@rz.uni-regensburg.de> wrote:
> I probably forgot to mention the obvious: My enhancement request was
> for cases where git would reject so split a hunk. I don't want to
> change the default split (if it finds a point to split).
> So maybe call it a "2nd-level-split". Only if split refuses to split,
> you could avoid using "edit" to manually split.
> I know that in general such things can't be right, but you can
> either reject the new hunks or use "edit". I just guessed the feature
> could save some time on the average.

FWIW, I would very much like a "2nd-level split" where it simply splits
into individual lines. I think it's not worth trying to be extra clever
about it. For your example, I'd simply want the following behavior:

  -AAA
  -BBB
  +CCC
  +DDD
  Stage this hunk? SPLIT

  -AAA
  Stage this hunk? YES

  -BBB
  Stage this hunk? NO

  +CCC
  Stage this hunk? YES

  +DDD
  Stage this hunk? NO

This would allow me to stage the following:

  -AAA
  +CCC

and leave the following unstaged:

  -BBB
  +DDD

but would also allow any other combination.


...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: Re: Extended splitting for "git add --interactive"

[Brandon McCaig]

Hello,

On Thu, Nov 27, 2014 at 5:14 AM, Johan Herland <johan@herland.net> wrote:
> FWIW, I would very much like a "2nd-level split" where it simply splits
> into individual lines. I think it's not worth trying to be extra clever
> about it. For your example, I'd simply want the following behavior:
>
>   -AAA
>   -BBB
>   +CCC
>   +DDD
>   Stage this hunk? SPLIT
>
>   -AAA
>   Stage this hunk? YES
>
>   -BBB
>   Stage this hunk? NO
>
>   +CCC
>   Stage this hunk? YES
>
>   +DDD
>   Stage this hunk? NO
>
> This would allow me to stage the following:
>
>   -AAA
>   +CCC
>
> and leave the following unstaged:
>
>   -BBB
>   +DDD
>
> but would also allow any other combination.

Having (e)dited a lot of hunks manually I can see it being a bit
difficult to understand line-by-line (but then I rarely split as it
rarely does what I need so I'm not sure what use cases this would
apply). I just had an idea about re-joining added lines in the output
each time to show you what you're actually doing to the hunk with each
prompt. I don't know if it's a good idea. Illustration:

 AAA
 BBB
-CCC
-DDD
+EEE
+FFF
 GGG
Stage this hunk? s

  AAA
  BBB
- CCC
Stage this hunk? y

  AAA
  BBB
 -CCC
- DDD
Stage this hunk? n

  AAA
  BBB
 -CCC
  DDD
+ EEE
Stage this hunk? y

  AAA
  BBB
 -CCC
  DDD
 +EEE
+ FFF
  GGG
Stage this hunk? n

In any case, I find that editing the hunk is generally faster than
trying to figure out if split is going to do something useful (perhaps
studying the Git code would help in that regard).

That said, the key to making editing the hunk (or patches in general)
efficient is adding keybindings to your favorite editor to edit
unified diffs. In my Vim configuration I map ,, to a function that
removes the current line change (removes - line, deletes + line) and
,. to add - to context lines. Both also always move down a line
automatically and center that line on the screen, and have no effect
on lines for which the chosen function has no meaning. So editing a
hunk typically becomes ,, to remove unwanted changes from the current
hunk or skip context lines and j to skip good lines to get to the next
changes. Occasionally I use ,. to remove a context line that was in my
original source. And if I want to invent a + line it's just o or O.
The bit I'm editing remains in the middle of my screen with my whole
screen for context. My relevant vimrc:

autocmd FileType diff
            \ nnoremap ,, :call UndoPatch()<CR>|
            \ nnoremap ,. :s/^ /-/e<CR>:nohl<CR>jzz

function! UndoPatch()
    normal! 0

    if getline('.') =~ '^+'
        delete
        normal! zz
        return
    endif

    if getline('.') =~ '^-'
        s/^-/ /
        nohlsearch
    endif

    normal! j
    normal! ^
    normal! zz
endfunction

Maybe that'll be useful for somebody else. Any editor suitable for a
programmer will be able to do something similar. I suspect that
customizing your editor will be time better spent.

Regards,


-- 
Brandon McCaig <bamccaig@gmail.com> <bamccaig@castopulence.org>
Castopulence Software <https://www.castopulence.org/>
Blog <http://www.bambams.ca/>
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q{Vg qbrfa'\''g nyjnlf fbhaq gung jnl.};
tr/A-Ma-mN-Zn-z/N-Zn-zA-Ma-m/;say'