Re: [PATCH 4/4] am: fix --interactive HEAD tree resolution

From: Jeff King <peff@peff.net>
Date: May 24, 2019, 06:39 UTC
Message-ID: <20190524063955.GD25694@sigill.intra.peff.net>
In-Reply-To: <nycvar.QRO.7.76.6.1905230858570.46@tvgsbejvaqbjf.bet>

On Thu, May 23, 2019 at 09:12:27AM +0200, Johannes Schindelin wrote:

Show 13 quoted lines

> > +	if (!get_oid("HEAD", &head)) {
> > +		struct object *obj;
> > +		struct commit *commit;
> > +
> > +		obj = parse_object_or_die(&head, NULL);
> > +		commit = object_as_type(the_repository, obj, OBJ_COMMIT, 0);
> > +		if (!commit)
> > +			die("unable to parse HEAD as a commit");
> 
> Wouldn't this be easier to read like this:
> 
> 		struct commit *commit =
> 			lookup_commit_reference(the_repository, &head);

Just the first two lines, I assume you mean; we still have to die ourselves. There is a lookup_commit_or_die(), but weirdly it warns if there was any tag dereferencing. I guess that would never happen here, since we're reading HEAD (and most of the existing calls appear to be for HEAD). So I'll go with that.

Show 11 quoted lines

> > +test_expect_success 'interactive am can apply a single patch' '
> > +	git reset --hard base &&
> > +	printf "%s\n" y n | git am -i mbox &&
> 
> Since we want contributors to copy-edit our test cases (even if they do
> not happen to be Unix shell scripting experts), it would be better to
> write
> 
> 	test_write_lines y n | git am -i mbox &&
> 
> here. Same for similar `printf` invocations further down.

I think test_write_lines is mostly about avoiding echo chains, but it's probably a little more readable to avoid having to say "\n". I'll adopt that.

Show 18 quoted lines

> > +	echo no-conflict >expect &&
> > +	git log -1 --format=%s >actual &&
> > +	test_cmp expect actual
> 
> I would prefer
> 
> 	test no-conflict = "$(git show -s --format=%s HEAD)"
> 
> or even better:
> 
> test_cmp_head_oneline () {
> 	if test "$1" != "$(git show -s --format=%s HEAD)"
> 	then
> 		echo >&4 "HEAD's oneline is '$(git show -s \
> 			--format=%s HEAD)'; expected '$1'"
> 		return 1
> 	fi
> }

This, I disagree with. IMHO comparing command output using "test" is harder to read and produces worse debugging output (unless you do a helper as you showed, which I think makes the readability even worse). Not to mention that it raises questions of the shell's whitespace handling (though that does not matter for this case).

What's your complaint with test_cmp? Is it the extra process? Could we perhaps deal with that by having it use `read` for the happy-path?

Or do you prefer having a one-liner? I'd rather come up with a more generic helper to cover this case, that can run any command and compare it to a single argument (or stdin). E.g.,:

  test_cmp_cmd no-conflict git log -1 --format=%s

or

  test_cmp_cmd - git foo <<-\EOF
  multi-line
  expectation
  EOF

But I'd rather approach those issues separately and systematically, and not hold up this bug fix.

Show 9 quoted lines

> > +test_expect_success 'interactive am can resolve conflict' '
> > +	git reset --hard base &&
> > +	printf "%s\n" y y | test_must_fail git am -i mbox &&
> > +	echo resolved >file &&
> > +	git add -u &&
> > +	printf "%s\n" v y | git am -i --resolved &&
> 
> Maybe a comment, to explain to the casual reader what the "v" and the "y"
> are supposed to do?

OK. The "v" is actually optional, but I figured it would not hurt to have us print the patch we just generated. I'll add a comment.

> After wrapping my head around the intentions of these commands, I agree
> that they test for the right thing.

Thanks!

-Peff