Re: [PATCH v2] Fix notes handling in rev-list

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 17, 2012, 05:42 UTC
Message-ID: <7vvchnx7tc.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20120717034640.GB20945@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 53 quoted lines

> On Mon, Jul 16, 2012 at 09:30:09PM +0300, Jukka Lehtniemi wrote:
>
>> @@ -111,6 +112,7 @@ static void show_commit(struct commit *commit, void *data)
>>  		ctx.date_mode = revs->date_mode;
>>  		ctx.date_mode_explicit = revs->date_mode_explicit;
>>  		ctx.fmt = revs->commit_format;
>> +		ctx.show_notes = revs->show_notes;
>>  		pretty_print_commit(&ctx, commit, &buf);
>>  		if (revs->graph) {
>>  			if (buf.len) {
>
> Makes sense. We were just failing to propagate the show_notes flag to
> the pretty-print code, as log-tree does.
>
>> @@ -159,6 +161,12 @@ static void show_commit(struct commit *commit, void *data)
>>  	} else {
>>  		if (graph_show_remainder(revs->graph))
>>  			putchar('\n');
>> +		if (revs->show_notes_given) {
>> +			struct strbuf buf = STRBUF_INIT;
>> +			format_display_notes(commit->object.sha1, &buf, 0, NOTES_SHOW_HEADER|NOTES_INDENT); 
>> +			fwrite(buf.buf, 1, buf.len, stdout);
>> +			strbuf_release(&buf);
>> +		}
>
> But why are we using show_notes_given here instead of show_notes? The
> former is about "did we get any kind of --notes option on the
> command-line". So doing "git rev-list --no-notes" would trigger it,
> which seems wrong. We should simply be checking show_notes again, no?
>
> Also, it seems odd to me to show the notes after graph_show_remainder.
> Your first hunk is about passing the notes option to the pretty-printer,
> which handles graph output already, and looks like this:
>
>   $ git rev-list --oneline --graph --notes -2 HEAD
>   * f6bbb09 Fix notes handling in rev-list
>   | Notes:
>   |     foobar
>   | 
>   * 31c7954 Update draft release notes for 7th batch
>
> Just like log, the notes are part of the commit information to the right
> of the graph. But this second hunk is for when we are not using the
> pretty-printer at all, and the output looks like this:
>
>   $ git rev-list --graph --notes -2 HEAD
>   * f6bbb09529a4cc73446c7c115ac1468477bd0cc6
>
>   Notes:
>       foobar
>   * 31c79549b85c6393be4f40432f5b86ebc097fc7e
>
> which doesn't make sense

I actually have quite a different feeling about this. As I said in the separate message, I think --graph, or anything that makes the output unparsable or harder to parse for machines for that matter, in rev-list are not something we have because we wanted to support them, but that which just happen to work because the large part of rev-list and log can share building blocks to do similar things. The key phrase is "can share" here; it does not necessarily mean they "should" [*1*].

First and foremost, rev-list is a tool for people who hate what our vanilla "git log" Porcelain does enough that they want to write their own Porcelain scripts using it.

I do not mind having an option to show the notes text, but I doubt it is a sane thing to do to make "rev-list --notes" unconditionally show the payload of the notes blob. "rev-list --objects" only shows the object names of trees and blobs, not the payload in these objects, and this is very much on purpuse. It allows the downstream process that reads its output from the pipe to easily parse the output and choose to do whatever it wants to do using them.

I wonder if we should show the blob object names that store the notes payload if we were given --notes option in a format that is easy for readers to mechanically parse its output.

In any case, the use of format_display_notes() that is meant for human consumption feels very wrong to me, especially it seems to be placed outside the "if (revs->verbose_header && commit->buffer)" block in this patch. I do not have any problem if the patch makes the notes text shown in the other side of the if block that uses pretty_print_commit(), though.

[Footnote]

*1* A simple litmus test is to ask this question: if somebody comes
    up with a "better" way to show the same output for the option,
    would we accept that update without worrying about breaking
    existing scripts?  If the answer is yes, that is a secondary
    feature in the context of "rev-list" plumbing like --graph is.