Subject: Re: [PATCH v2] add -p: fix 2.17.0-rc* regression due to moved code

From: [email-masked] (Ævar Arnfjörð Bjarmason)
Date: Sat, 31 Mar 2018 19:13:40 +0200

On Sat, Mar 31 2018, Phillip Wood wrote:

> On 31/03/18 13:50, Ævar Arnfjörð Bjarmason wrote:
>> Fix a regression in 88f6ffc1c2 ("add -p: only bind search key if
>> there's more than one hunk", 2018-02-13) which is present in
>> 2.17.0-rc*, but not 2.16.0.
>>
>> In Perl, regex variables like $1 always refer to the last regex
>> match. When the aforementioned change added a new regex match between
>> the old match and the corresponding code that was expecting $1, the $1
>> variable would always be undef, since the newly inserted regex match
>> doesn't have any captures.
>>
>> As a result the "/" feature to search for a string in a hunk by regex
>> completely broke, on git.git:
>
> Good catch, I could have sworn I'd tested my patch but I obviously
> didn't notice the warning (I've got interactive.singlekey set so it
> prints the warning and then prompts as it always has done). Calling it
> completely broken is perhaps a little harsh as it does work if you
> enter the regex again and with interactive.singlekey set you only have
> to enter the regex once.

To clarify by "completely broken" I mean the "/" feature itself, but
yeah, you can still search by regex since we just so happen to have the
fallback codepath intended to catch "/" without an accompanying string,
which'll kick in and ask you for the regex since $1 will be undef at
that point, and will thus coerce stringwise to "".

> Thanks for fixing it
>
> Phillip
>>
>>      $ perl -pi -e 's/Git/Tig/g' README.md
>>      $ ./git --exec-path=$PWD add -p
>>      [..]
>>      Stage this hunk [y,n,q,a,d,j,J,g,/,s,e,?]? s
>>      Split into 4 hunks.
>>      [...]
>>      Stage this hunk [y,n,q,a,d,j,J,g,/,s,e,?]? /Many
>>      Use of uninitialized value $1 in string eq at /home/avar/g/git/git-add--interactive line 1568, <STDIN> line 1.
>>      search for regex? Many
>>
>> I.e. the initial "/regex" command wouldn't work, and would always emit
>> a warning and ask again for a regex, now it works as intended again.
>>
>> Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
>> ---
>>
>> Of course I just noticed the grammar errors in the commit message
>> after sending. Here's a v2 with that fixed, also genreated the patch
>> with -U6 to make it clear what's going on.
>>
>>   git-add--interactive.perl | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/git-add--interactive.perl b/git-add--interactive.perl
>> index d190469cd8..c1f52e457f 100755
>> --- a/git-add--interactive.perl
>> +++ b/git-add--interactive.perl
>> @@ -1561,13 +1561,13 @@ sub patch_update_file {
>>   			elsif ($line =~ m|^/(.*)|) {
>>   				my $regex = $1;
>>   				unless ($other =~ m|/|) {
>>   					error_msg __("No other hunks to search\n");
>>   					next;
>>   				}
>> -				if ($1 eq "") {
>> +				if ($regex eq "") {
>>   					print colored $prompt_color, __("search for regex? ");
>>   					$regex = <STDIN>;
>>   					if (defined $regex) {
>>   						chomp $regex;
>>   					}
>>   				}
>>