Re: [PATCH] pretty: add format specifiers: %gr, %gt, %gI, gi

From: Theodore Ts'o <tytso@mit.edu>
Date: Jul 11, 2016, 16:43 UTC
Message-ID: <20160711164317.GB3890@thunk.org>
In-Reply-To: <20160711050201.GA18031@sigill.intra.peff.net>

On Mon, Jul 11, 2016 at 01:02:02AM -0400, Jeff King wrote:

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> Yeah, I'd have hoped for %gd, as well. One thing I think we should move
> towards in the long run is giving more readable names to our
> placeholders for git-log, the way for-each-ref and cat-file do (but
> keeping the existing ones for compatibility and as a shorthand).
> 
> So ideally the answer in the long run is:
> 
>   %(reflog-ref)@{%(reflog-index)}
> 
> or possibly:
> 
>   %(reflog:index)
> 
> for the whole thing. Or something like that. I haven't thought that hard
> about the exact syntax.

Yes, FWIW, I agree that long term, using % followed by one or two characters is just a mess, and using some kind of human-readable format is going to make a lot of sense. I can imagine a few places where I might still want to type --format=%at in some kind of ad-hoc shell command, but in most places, if you're using a complex --format specifier, it's going either in a shell script or in a .gitconfig file, where being verbose is probably more of an advantage than a disadvantage.

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>   1. It's half-implemented. Why can we do format X, but not format Y
>      (for that matter, why can you do %ct, but there is no --date format
>      that matches it?). That sort of non-orthogonality ends up
>      frustrating for users and makes git look creaky and poorly thought
>      out.

Git *is* creaky and not thought-out in advance; that's just the nature of how most successful open source projects grow; might as well be proud of it. :-) As Greg K-H has said: "We believe in evolution, and not intelligent design." :-)

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> > ... although I doubt whether git would ever want to do the equivalent of:
> > 
> > gcloud compute images list  --format='table[box,title=Images](name:sort=1,family)'
> > 
> > which will print something like this:
> 
> That's neat, though I think I'd really prefer just making it easy to get
> the data out of git in a structured way, and then applying some cool
> json-formatting script to it. Surely "turn this json into a table" is a
> thing that could be solved once for everybody (I don't work with it
> enough to know, but maybe "jq" can do that already).

Oh, agreed. I used that as over-the-top example of something we probably wouldn't want to put in the git core. jq can't, but I'm sure there must be some JSON tool out there which can.

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> But let's get back to reality for a moment. Here are some patches that
> address the issues you brought up above.
> 
>   [1/5]: doc/rev-list-options: clarify "commit@{Nth}" for "-g" option
>   [2/5]: doc/rev-list-options: explain "-g" output formats
>   [3/5]: doc/pretty-formats: describe index/time formats for %gd
>   [4/5]: date: document and test "raw-local" mode
>   [5/5]: date: add "unix" format
> 
> The next step is either:
> 
>   - add specific reflog-time-formats, as your patch does
> 
>   - add a generic reflog-date placeholder, so you can do:
> 
>       git log --date=unix --format='%gT'
> 
>     or whatever. That still doesn't give you multiple date types in a
>     single invocation, though. It's probably not much code to do so, but
>     designing the syntax and supporting existing placeholders would be
>     some work.
> 
> I'm on the fence, so I'll let you decide how you want to proceed. I can
> live with "%gr" and "%gt", as they are at least symmetric with their
> author/committer counterparts.

I'm on the fence myself. I can live with either, since either way the long message command line will be going in .gitconfig. I have a slight preference for %gr and %gt, as %gT isn't orthogonal with %ad/%cd, but I could be easily pursuaded otherwise.

Does anyone else have a strong opinion?

						- Ted