ignore blank line removals

ignore blank line removals

[John Rood]

If the contents of a file initially are:
  one

  three
and on branch A there is a commit, removing the blank line:
  one
  three
and on branch B there is a commit, adding 'two':
  one
  two
  three
Normally, if you try to merge A into B (or B into A), git recognizes a
decision needs to be made between removing the second line or add
"two" to the second line. It would be convenient to have a merge
strategy that defaults to the latter in cases where the removed line
was a blank line (or a line containing only whitespace) ...something
like -Xignore-blank-line-removals.

Re: ignore blank line removals

[John Rood]

Is there any push-back on this, or is there a backlog that we can add
this feature to?

On Thu, Nov 3, 2016 at 10:57 AM, John Rood <mr.john.rood@gmail.com> wrote:
> If the contents of a file initially are:
>   one
>
>   three
> and on branch A there is a commit, removing the blank line:
>   one
>   three
> and on branch B there is a commit, adding 'two':
>   one
>   two
>   three
> Normally, if you try to merge A into B (or B into A), git recognizes a
> decision needs to be made between removing the second line or add
> "two" to the second line. It would be convenient to have a merge
> strategy that defaults to the latter in cases where the removed line
> was a blank line (or a line containing only whitespace) ...something
> like -Xignore-blank-line-removals.

Re: ignore blank line removals

[Junio C Hamano]

John Rood <mr.john.rood@gmail.com> writes:

> On Thu, Nov 3, 2016 at 10:57 AM, John Rood <mr.john.rood@gmail.com> wrote:
>> If the contents of a file initially are:
>>   one
>>
>>   three
>> and on branch A there is a commit, removing the blank line:
>>   one
>>   three
>> and on branch B there is a commit, adding 'two':
>>   one
>>   two
>>   three
>> Normally, if you try to merge A into B (or B into A), git recognizes a
>> decision needs to be made between removing the second line or add
>> "two" to the second line. It would be convenient to have a merge
>> strategy that defaults to the latter in cases where the removed line
>> was a blank line (or a line containing only whitespace) ...something
>> like -Xignore-blank-line-removals.
>
> Is there any push-back on this, or is there a backlog that we can add
> this feature to?

If you mean by "push-back" objections that say "this feature is evil
and should not be added to Git, ever", I do not think we saw any on
the list.  The lack of response is most likely that everybody
thought "Meh." aka "It is not useful/interesting/valuable enough
feature to bother discussing."

One thing I wondered was what you would want if the contents were
one/three without blank, A added blank between the two and B
replaced blank with two.  As your example shows, in the filetype you
are dealing with, a blank line has no significant meaning (otherwise
you won't be ignoring the change A made to remove the blank in your
original example).  The outcome desired by you may be one/two/three
without any blank in that case because of that.  Which would lead to
the suspicion that ignore-blank-line-removals is not a good general
feature (i.e. in this other example, you want to ignore blank line
addition).  Which further leads to the suspicion that the desire you
expressed in the original post is not well thought through to be a
useful specifification to build anything out of (yet), but is merely
a potentially interesting discussion starter.  And nobody so far
found it interesting enough to spend time discussing it further to
make the wish detailed enough to be called a "design" of a new
feature.

Having said all that.

I suspect that you may not have to make any change to Git to do what
you want; can't you just use the 'merge' attribute with a custom
3-way merge driver that removes an empty line?

Re: ignore blank line removals

[John Rood]

Yes that makes sense.
I was not aware of custom merge drivers, but indeed that may address
my situation. I'll look into it.
Thanks!

On Tue, Nov 15, 2016 at 12:51 PM, Junio C Hamano <gitster@pobox.com> wrote:
> John Rood <mr.john.rood@gmail.com> writes:
>
>> On Thu, Nov 3, 2016 at 10:57 AM, John Rood <mr.john.rood@gmail.com> wrote:
>>> If the contents of a file initially are:
>>>   one
>>>
>>>   three
>>> and on branch A there is a commit, removing the blank line:
>>>   one
>>>   three
>>> and on branch B there is a commit, adding 'two':
>>>   one
>>>   two
>>>   three
>>> Normally, if you try to merge A into B (or B into A), git recognizes a
>>> decision needs to be made between removing the second line or add
>>> "two" to the second line. It would be convenient to have a merge
>>> strategy that defaults to the latter in cases where the removed line
>>> was a blank line (or a line containing only whitespace) ...something
>>> like -Xignore-blank-line-removals.
>>
>> Is there any push-back on this, or is there a backlog that we can add
>> this feature to?
>
> If you mean by "push-back" objections that say "this feature is evil
> and should not be added to Git, ever", I do not think we saw any on
> the list.  The lack of response is most likely that everybody
> thought "Meh." aka "It is not useful/interesting/valuable enough
> feature to bother discussing."
>
> One thing I wondered was what you would want if the contents were
> one/three without blank, A added blank between the two and B
> replaced blank with two.  As your example shows, in the filetype you
> are dealing with, a blank line has no significant meaning (otherwise
> you won't be ignoring the change A made to remove the blank in your
> original example).  The outcome desired by you may be one/two/three
> without any blank in that case because of that.  Which would lead to
> the suspicion that ignore-blank-line-removals is not a good general
> feature (i.e. in this other example, you want to ignore blank line
> addition).  Which further leads to the suspicion that the desire you
> expressed in the original post is not well thought through to be a
> useful specifification to build anything out of (yet), but is merely
> a potentially interesting discussion starter.  And nobody so far
> found it interesting enough to spend time discussing it further to
> make the wish detailed enough to be called a "design" of a new
> feature.
>
> Having said all that.
>
> I suspect that you may not have to make any change to Git to do what
> you want; can't you just use the 'merge' attribute with a custom
> 3-way merge driver that removes an empty line?
>