Re: visualizing Git's Git repo

On Mon, 26 May 2008, Joshua Haberman wrote:

I would seriously suggest avoiding "--date-order" unless you have some deep reason to see how the commits on different development paths relate to each other date-wise - something you should normally not have.

The thing is, --date-order strings out and mixes up the commits on the same development chain, and by doing so it makes the different chains of development much harder to see. It also ends up showing the development in a more "parallel" way, which in turn makes the view even harder to read.

So I would suggest not using --date-order by default. It doesn't add anything to any normal flow, and it makes the big picture harder to see.

The only time you really want --date-order (or "-d", which is shorthand for it for just gitk) is really

 - when the big picture is really really simple, and you actually want to 
   see more detail because the big picture is too trivial to even be 
   interesting otherwise.

   (In other words: --date-order is fine for really simple development 
   where there is only ever just a couple of branches or where you have 
   pruned away so much of the history that the remaining part is simple)

 - when you want to debug "git rev-list" behaviour itself, since the date 
   order actually matters for how git traverses the commit chains.

The second case is something that I suspect nobody but me and a few other people have ever done. I found it very useful together with --show-all when I was debugging the revision walker (see commits

	3131b713013f06285cad3ffdcc61f417ac4ba158
	7d004199d134c9d465e013064f72dbc04507f6c0

where the first implements --show-all, and the second one is the end result of my debugging).

In other words: never start out with "-d" or "--date-order" by default. Only if you have some reason to then think that the view is too simple or you need to drill down into the commit relationships should you use it.

I use "gitk" almost every time when I pull from anybody in the kernel. I tend to do it with git itself, when I update from Junio. The most common arguments I use is

	gitk ORIG_HEAD..

or

	gitk @{12.hours.ago}..

where the latter in particular is very nice to see an overview of "ok, what did I pull today".

And I basically *never* use --date-order, nor do I often look at more than one single branch.

The one special case is when merging, and there are conflicts. In that case, I often look at two branches, and I often do

	gitk MERGE_HEAD... <filenames>

to see the symmetric difference (actually, I usually just do "gitk --merge" which is just shorthand for the above). And in that case, I do occasionally add a "-d", because that shows what the relative timing were for the commits, which is sometimes interesting information (ie if there are clashes, which commit is the more recently committed one can actually be somewhat relevant - although it's rare).

So in that case I look at two branches (the one I'm on, and the one I'm merging), and the "..." format means that I ignore everything that is common to them.

For the kernel, there's been a lot of discussion about why I prefer people to rebase vs merge (or often - *avoiding* merges entirely), see the kernel mailing list, and search for merging. There was a thread (subject: "[alsa-devel] HG -> GIT migration") about a week ago where I tried to explain my opinions about about some of this.

		Linus