Highlighting for log & graphlog - mercurial_devel

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Message from discussion Highlighting for log & graphlog
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Subject: Re: [PATCH 0 of 3] Highlighting for log & graphlog
From: Matt Mackall <m...@selenic.com>
To: peter.arrenbre...@gmail.com
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Date: Wed, 04 May 2011 16:10:37 -0500
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Cc: Mercurial Devel <mercurial-de...@selenic.com>,
	Christiansen <dan...@gmail.com>, D...@waste.org,
	Alexander Solovyov <pira...@piranha.org.ua>
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On Wed, 2011-05-04 at 16:34 +0200, Peter Arrenbrecht wrote:
> On Tue, May 3, 2011 at 10:26 PM, Matt Mackall <m...@selenic.com> wrote:
> > On Tue, 2011-05-03 at 22:00 +0200, Benoit Boissinot wrote:
> >> On Tue, May 3, 2011 at 9:52 PM, Matt Mackall <m...@selenic.com> wrote:
> >> > On Tue, 2011-05-03 at 21:45 +0200, Benoit Boissinot wrote:
> >> >>
> >> >> It is nice for example with "outgoing()", I can easily see how the
> >> >> outgoing csets fit into the whole graph.
> 
> I'm the one who suggested the feature. It was triggered by Benoit's
> suggestion that we have a "sample(undecidedset)" revset to visualize
> how set discovery takes samples. But there's other uses. Basically, it
> boils down to being able to see things in context:
> 
>  * Where was this file touched, on what lines development?
>  * Same for authors.
>  * Highlight all ancestors/descendants of this node.
>  * Highlight this named branch.
> 
> In fact, I think we should maybe revisit the decision to try and align
> log and glog. log is very much about speed and thus always walks the
> changelog in revnum order. For glog, however, I think we should value
> versatility over raw speed. It's a DAG visualizer. Once we see it as
> such, we can do things like:
> 
>  * Walk from all heads in breadth-first manner to get an overview of
> what the heads are (maybe not exactly breadth-first, but a couple of
> nodes at a time).
>  * Use the linearizing toposort of shrink-revlog and combine it with
> the elision of linear runs (an old patch of mine) to get a concise
> overview of branching/merging in a tree.
> 
> glog is very much about DAGs. I already took a first step in the
> direction of making DAGs first class with dagutil.py (introduced by
> set discovery). Benoit is working on moving the shrink-revlog toposort
> there. Maybe we could also move Patrick's "redagging" (rebuilding a
> DAG from a disconnected revset) there. So the more general DAG algos
> would be clearly separate from visualizing them.

Teaching revlog's sort() about toposort might be useful.

> Then we could base glog on the DAGs exposed by dagutil. And we could
> also easily add support for other visualizers like dot (which should
> be configurable so it immediately launches a renderer and viewer) and
> hgweb.
> 
> This way, glog and other visualizers could make the power of revsets
> even more awesome.

I'm all for making glog cool. But I disagree about aligning it with log.
People are going to continue to expect feature parity with log where it
makes sense. And the current implementation of log is horrendous to the
point where it's no longer maintainable. By being reimplemented in terms
of revsets, I think graphlog has already passed it up.

Check this out:

$ time hg log -b stable -q | wc
   1238    1238   23481

real	0m2.564s
user	0m2.413s
sys	0m0.100s

$ time hg log -r 'branch(stable)' -q | wc
   1238    1238   23481

real	0m2.145s
user	0m2.040s
sys	0m0.073s

Revsets are faster (and much more powerful) than log's engine, and
that's even before the optimizer has gotten the chance to do anything
clever. The current log code wants to die, though we'll need to teach
revsets a bit about the file fast path first.

> >> > It's kind of problematic to me that on a stock install (ie color not
> >> > enabled), -H is a no-op. If we do something like this, it should a) have
> >> > a meaningful non-color effect and b) have an appropriate non-color name.
> >> > See <em> vs <i> in HTML for comparison.
> >>
> >> If you don't have color enabled, you won't see -H.
> >
> > Then I'd say it's too invasive of the core. Either it's general-purpose
> > or it shouldn't be making the log core even hairier.
> 
> It could, for instance, use a different node character like * for
> highlighted nodes (like we use @ today for the dirstate parents). Or
> we could allow folks to specify a prefix to use for the next text,
> with a default taken from graphlog.highlightprefix.

Ok, let's figure that out. Here's a plan of attack:

- come up with a display-neutral name for the feature (compare <em> and
<i> in HTML)
- come up with a sensible way to display emphasized changesets (or
whatever we call them) in plain text
- implement the color part of it

Note that whatever we do for plain text (ie prefix with a * or indent or
whatever), we'll probably need to preserve when we turn color on to
minimize surprise.

Just so we have a concrete proposal to discuss, here's my take on '*'
prefixing:

o    changeset:   14183:333def42e785
|\   tag:         qparent
| |  parent:      14181:bf951d58b917
| |  parent:      14182:ec5886db9dc6
| |  user:        Matt Mackall <m...@selenic.com>
| |  date:        Wed May 04 08:21:50 2011 -0500
| |  summary:     merge with crew
| |
| o  * changeset:   14182:ec5886db9dc6
| |  * parent:      14160:fa2b596db182
| |  * user:        Sune Foldager <c...@cyanite.org>
| |  * date:        Wed May 04 13:37:41 2011 +0200
| |  * summary:     tests: fix deprecated use of hg debugdata/debugindex
| |
o |    changeset:   14181:bf951d58b917
|\ \   parent:      14180:1123bbba278d
| | |  parent:      14159:31ec4d7eb63f
| | |  user:        Matt Mackall <m...@selenic.com>
| | |  date:        Tue May 03 22:04:23 2011 -0500
| | |  summary:     merge with stable

There are other possibilities like adding a new column 0:

  o    changeset:   14183:333def42e785
  |\   tag:         qparent
  | |  parent:      14181:bf951d58b917
  | |  parent:      14182:ec5886db9dc6
  | |  user:        Matt Mackall <m...@selenic.com>
  | |  date:        Wed May 04 08:21:50 2011 -0500
  | |  summary:     merge with crew
  | |
* | o  changeset:   14182:ec5886db9dc6
* | |  parent:      14160:fa2b596db182
* | |  user:        Sune Foldager <c...@cyanite.org>
* | |  date:        Wed May 04 13:37:41 2011 +0200
* | |  summary:     tests: fix deprecated use of hg debugdata/debugindex
  | |
  o |    changeset:   14181:bf951d58b917
  |\ \   parent:      14180:1123bbba278d
  | | |  parent:      14159:31ec4d7eb63f
  | | |  user:        Matt Mackall <m...@selenic.com>
  | | |  date:        Tue May 03 22:04:23 2011 -0500
  | | |  summary:     merge with stable

-- 
Mathematics is the supreme nostalgia of our time.


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