[PATCH] revset: add regular expression support to 'desc()'

[Matt Harbison]

On Sat, 07 Jan 2017 22:55:02 -0500, Sean Farley <sean at farley.io> wrote:

> Matt Harbison <mharbison72 at gmail.com> writes:
>
>> # HG changeset patch
>> # User Matt Harbison <matt_harbison at yahoo.com>
>> # Date 1483842392 18000
>> #      Sat Jan 07 21:26:32 2017 -0500
>> # Node ID 7347f75339503a8266285ac12412ac5f104d4df0
>> # Parent  4ab19763d71c2bb9a239dff523b18ed860e34563
>> revset: add regular expression support to 'desc()'
>>
>> The legacy behavior of doing a case insensitive match for literals is  
>> preserved
>> for BC.  This includes with the new 'literal:' prefix for user  
>> simplicity.
>>
>> There are two other revsets that do case insensitive matches- 'user()'  
>> (and its
>> alias 'author()'), and 'keyword()'.  The 'keyword()' predicate only  
>> supports
>> literals, so its behavior isn't interesting right now.  The 'user()'  
>> predicate
>> is documented to support regex, but ends up lowercasing both the needle  
>> and the
>> haystack, effectively making it a case insensitive regex.  That  
>> surprised me,
>> since it's the only instance of that behavior.  I'm not sure if this  
>> should
>> conform to that because we are stuck with BC, or if that should be  
>> considered a
>> bug and changed.  If we can't change it, that probably precludes adding  
>> an
>> insensitive regex matcher [1].
>>
>> [1]  
>> https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-January/092070.html
>
> I was a bit confused before because I was mixing up templates with
> revsets. If I follow your previous patch, you want to have a revset that
> just searches the first line of the description, correct?

Correct.

> If that's correct, it would seem that our choices with template
> functionality might be a precedent for this, no?

Ideally. But I'm not sure how to apply that here.  Are you suggesting a  
new predicate 'firstline()' (instead of 'summary')?  I assumed the  
template filter was generically named because it's a generic filter  
(though realistically I'm not sure what else you would want to limit to  
the first line).

If you mean the filtering functionality ("{desc|firstline}"), I'm not sure  
how that helps.  Obviously you can filter _revisions_ by chaining  
predicates, but what this needs to do is narrow down the _field_ being  
tested within one predicate.  I don't know of any revset mechanism to do  
that.