Implementing hg log --graph --follow-first

[Matt Mackall]

On Sat, 2012-02-25 at 16:15 +0100, Patrick Mézard wrote:
> Hello,
> 
> commands.log() implements a --follow-first option:
> 
>   ('', 'follow-first', None,
>      _('only follow the first parent of merge changesets (DEPRECATED)')),
> 
> It was deprecated in:
> 
>   changeset:   15407:e4a17bb8472f
>   parent:      15404:c1eb8398fe82
>   user:        Matt Mackall <mpm at selenic.com>
>   date:        Wed Nov 02 15:06:40 2011 -0500
>   summary:     log: hide some low-utility options

> which looks more like hiding than deprecating.

First note that 'deprecated' stopped meaning 'scheduled for removal' for
Mercurial a long ago. It now just means 'strongly discouraged'.

>  My problem is to support this option in graphlog, meaning supporting
> it in revsets. follow() revset currently calls filectx.ancestors(), so
> it would mean adding an "onlyfirst=False" option to
> filectx.ancestors() and workingfilectx.ancestors(). I would rather
> know if we intend to really deprecated this option and emit a warning
> like "--follow-first is not longer supported, falling back to
> --follow" instead.

Probably the right way to do it is to hand-roll a hidden _followfirst
revset method that iterates on [f]ctx.p1(). Nothing else will ever want
onlyfirst.

-- 
Mathematics is the supreme nostalgia of our time.