[PATCH 4 of 4 v3] log: add -L/--line-range option to follow file history by line range

[Yuya Nishihara]

On Mon, 16 Oct 2017 20:56:29 +0200, Denis Laxalde wrote:
> Augie Fackler a écrit :
> > (+jordigh, themystic, indygreg in case one of them has an opinion or inspiration)
> > 
> >> On Oct 13, 2017, at 10:24 AM, Yuya Nishihara <yuya at tcha.org> wrote:
> >>
> >> On Fri, 13 Oct 2017 10:02:07 +0200, Denis Laxalde wrote:
> >>> Yuya Nishihara a écrit :
> >>>> On Tue, 10 Oct 2017 17:37:27 +0200, Denis Laxalde wrote:
> >>>>> # HG changeset patch
> >>>>> # User Denis Laxalde <denis.laxalde at logilab.fr>
> >>>>> # Date 1507290475 -7200
> >>>>> #      Fri Oct 06 13:47:55 2017 +0200
> >>>>> # Node ID a05d3b45319a9ec28205f19dd7012b206a2b200f
> >>>>> # Parent  86a055d1c06f55daeb5d725187b61522974d24e3
> >>>>> # Available At http://hg.logilab.org/users/dlaxalde/hg
> >>>>> #              hg pull http://hg.logilab.org/users/dlaxalde/hg -r a05d3b45319a
> >>>>> # EXP-Topic followlines-cli/v2
> >>>>> log: add -L/--line-range option to follow file history by line range
> >>>>
> >>>> The series generally looks good to me in functionality POV. Some nits follow.
> >>>
> >>> Nits addressed in v4 which I can send now or once we agree on the UI.
> >>>
> >>>>
> >>>> So, do we really like this UI?
> >>>
> >>> For the record, there are currently two proposals:
> >>>
> >>> 1. The one implemented in this patch that adds a -L option to specify
> >>>     both the file and its line range:
> >>>
> >>>       hg log -L file.c,13-23 -L main.c,2-6
> >>>
> >>> 2. The idea by Yuya to have pairs of -L FROMLINE-TOLINE options and
> >>>     regular FILE arguments
> >>>
> >>>       hg log -L 13-23 file.c -L 2-6 main.c
> >>>
> >>>     The issue with this one (as explained in [1]) is that option parsing
> >>>     would not be strict, meaning that (IIUC) we would allow:
> >>>
> >>>       hg log -L 13-23 -L 2-6 file.c main.c
> >>>
> >>>     to work the same as the previous example.
> >>
> >> Thanks for the great summary. Some other crazy proposals just came up:
> >>
> >> 3. Extend the fileset syntax
> >>
> >>       hg log set:file.c at 13-23 set:main.c at 2-6
> >>
> >>     but we have to always type 'set:'
> >>
> >> 4. Reuse the matcher kind to carry linerange in pats
> >>
> >>       hg log file.c L:13-23 main.c L:2-6
> >>
> >>     linerange: and L: are preprocessed to be paired with the previous file
> >>     pattern.
> >>
> >> Another UI concern is whether --follow should be implied or required:
> >>
> >>   hg log -L file.c,13-23  (implies --follow)
> >>
> >> or
> >>
> >>   hg log -L file.c,13-23  (abort)
> >>   hg log --follow -L file.c,13-23
> >>
> >> If we take the latter, a plain file pattern can be used to select all lines.
> >>
> >>   hg log --follow -L file.c,13-23 main.c
> > 
> > I feel like the -L file.c,13-23 is the least ambiguous option in terms of understanding what a command *does*, and probably also the easiest to actually implement with our command line parser. The others feel clever in a way that kind of makes me nervous.

FWIW, I lean towards (1) -L file.c,13-23 syntax, but taking -L as the flag
to just attach linerange information, not the flag to enable followlines.

  hg log --follow -L FILE_A,LINERANGE_A FILE_B

will follow LINERANGE_A in FILE_A and the whole lines in FILE_B.

> > I guess that’s to say, +0 on that version, and I think my second choice is the fileset syntax option? None of these enthuse me, but I’d be enthusiastic about landing the feature *somehow*. I’m hesitant to not ship this series with 4.4, as it seems like this is just complicated enough we’ll have to do something that’s a compromise no matter what to make it work on the command line.
> > 
> 
> So, what should I do to move forward? I'd really like to get this in for
> 4.4. I'm happy to change anything, but need something actionable :)

I honestly don't want this "in" 4.4 as a stable option because log is one of
the most important command. Maybe it could be hidden by (EXPERIMENTAL) flag
if we really need to ship it with 4.4.

It's sad no one seems to be interested in this UI.