Re: [PATCH 2/2] builtin add -p: fix hunk splitting

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

Hi Ævar

On 20/12/2021 19:06, Ævar Arnfjörð Bjarmason wrote:
> 
> On Mon, Dec 20 2021, Phillip Wood via GitGitGadget wrote:
> 
>> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>>
>> To determine whether a hunk can be split a counter is incremented each
>> time a context line follows an insertion or deletion. If at the end of
>> the hunk the value of this counter is greater than one then the hunk
>> can be split into that number of smaller hunks. If the last hunk in a
>> file ends with an insertion or deletion then there is no following
>> context line and the counter will not be incremented. This case is
>> already handled at the end of the loop where counter is incremented if
>> the last hunk ended with an insertion or deletion. Unfortunately there
>> is no similar check between files (likely because the perl version
>> only ever parses one diff at a time). Fix this by checking if the last
>> hunk ended with an insertion or deletion when we see the diff header
>> of a new file and extend the existing regression test.
>>
>> Reproted-by: SZEDER Gábor <szeder.dev@gmail.com>
>> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>> ---
>>   add-patch.c                |  7 ++++++
>>   t/t3701-add-interactive.sh | 46 ++++++++++++++++++++++++++++++++++----
>>   2 files changed, 49 insertions(+), 4 deletions(-)
>>
>> diff --git a/add-patch.c b/add-patch.c
>> index 8c41cdfe39b..5cea70666e9 100644
>> --- a/add-patch.c
>> +++ b/add-patch.c
>> @@ -472,6 +472,13 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>>   			eol = pend;
>>   
>>   		if (starts_with(p, "diff ")) {
>> +			if (marker == '-' || marker == '+')
>> +				/*
>> +				 * Last hunk ended in non-context line (i.e. it
>> +				 * appended lines to the file, so there are no
>> +				 * trailing context lines).
>> +				 */
>> +				hunk->splittable_into++;
> 
> I wondered if factoring out these several "marker == '-' || marker ==
> '+'" cases in parse_diff() into a "is_plus_minus(marker)" was worth it,
> but probably not.

Yeah in the end I just factored out this hunk into a new function but I 
didn't add a function for "marker == '-' || marker ==
 > '+'"

>>   			ALLOC_GROW_BY(s->file_diff, s->file_diff_nr, 1,
>>   				   file_diff_alloc);
>>   			file_diff = s->file_diff + s->file_diff_nr - 1;
>> diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
>> index 77de0029ba5..94537a6b40a 100755
>> --- a/t/t3701-add-interactive.sh
>> +++ b/t/t3701-add-interactive.sh
>> @@ -326,7 +326,9 @@ test_expect_success 'correct message when there is nothing to do' '
>>   test_expect_success 'setup again' '
>>   	git reset --hard &&
>>   	test_chmod +x file &&
>> -	echo content >>file
>> +	echo content >>file &&
>> +	test_write_lines A B C D>file2 &&
> 
> style nit: "cmd args >file2" not "cmd args>file2"
> 
>> @@ -373,8 +411,8 @@ test_expect_success 'setup expected' '
>>   test_expect_success 'add first line works' '
>>   	git commit -am "clear local changes" &&
>>   	git apply patch &&
>> -	test_write_lines s y y | git add -p file 2>error >raw-output &&
>> -	sed -n -e "s/^([1-2]\/[1-2]) Stage this hunk[^@]*\(@@ .*\)/\1/" \
>> +	test_write_lines s y y s y n y | git add -p 2>error >raw-output &&
>> +	sed -n -e "s/^([1-9]\/[1-9]) Stage this hunk[^@]*\(@@ .*\)/\1/" \
>>   	       -e "/^[-+@ \\\\]"/p raw-output >output &&
>>   	test_must_be_empty error &&
>>   	git diff --cached >diff &&
> 
> style/diff nit: maybe worth it to in 1/2 do some version of:
> 
>      test_write_lines ... >lines &&
>      git ... <lines .. &&
>      ...
>      sed -n \
>      	-e ... \
>          -e ... \
>          >output
> 
> Just to make the diff smaller, i.e. just the "test_write_lines" line
> would be modified here.

In the end I decided to leave this as is, while refactoring slightly 
simplifies this patch it makes the previous one bigger and means that 
would need to be reviewed again.


> The changes themselves & this series LGTM.

Thanks

Best Wishes

Phillip