[PATCH V2] revset: add "matching" keyword

[Matt Mackall]

On Wed, 2012-04-04 at 00:56 +0200, Angel Ezquerra wrote:
> # HG changeset patch
> # User Angel Ezquerra <angel.ezquerra at gmail.com>
> # Date 1333282334 -7200
> # Node ID 3e65ae4b56dbc669c90613be40fb5b0f7cbe30e2
> # Parent  f350021ee32ed22b8bd7d3211a8899df0e3d6552
> revset: add "matching" keyword
> 
> This keyword can be used to find revisions that "match" one or more fields of a
> given set of revisions.
> 
> A revision matches another if all the selected fields (description, author,
> files, date, parents and/or substate) match the corresponding values of those
> fields on the source revision.
> 
> By default this keyword looks for revisions that whose metadata match
> (description, author and date) making it ideal to look for duplicate revisions.
> 
> matching takes 2 arguments (the second being optional):
> 
> 1.- rev: a revset represeting a _single_ revision (e.g. tip, ., p1(.), etc)
> 2.- [field(s) to match]: an optional field or list of fields to match.
>   By default matching will match the metadata fields (description, author and
>   date). When matching more than one field, they must be input as a list. When
>   matching a single field there is no need to surround it in () to make it a
>   list.
> 
> Examples:
> 
> 1.- Look for revisions with the same metadata (author, description and date)
> as the 11th revision:
> 
> hg log -r "matching(11)"
> 
> 2.- Look for revisions with the same description as the 11th revision:
> 
> hg log -r "matching(11, description)"
> 
> You do not need to type the whole 'description' word. You could also use
> 'descript' or 'desc' but not 'd' because 'd' also matches 'date' and 'date'
> takes prefecedence because fields are matched in alphabetical order.
> 
> 3.- Look for revisions with the same author as the current revision:
> 
> hg log -r "matching(., author)"
> 
> You could use 'user' rather than 'author' to get the same result.
> 
> 4.- Look for revisions with the same description _AND_ author as the tip of the
> repository:
> 
> hg log -r "matching(tip, (author, desc))"

This second arg is a bit weird. Subexpressions are normally revsets, so
this could confuse things like the optimizer and the alias engine.
Compare sort, which instead does:

sort(<some expression>, "author desc")

-- 
Mathematics is the supreme nostalgia of our time.