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From: Rasmus Villemoes <rv@rasmusvillemoes.dk>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
	Duy Nguyen <pclouds@gmail.com>, Taylor Blau <me@ttaylorr.com>
Subject: Re: [PATCH v2 1/3] help: redirect to aliased commands for "git cmd --help"
Date: Wed, 3 Oct 2018 08:24:14 +0200	[thread overview]
Message-ID: <9ab3d69a-033a-e5a0-7459-c6ba8a2ec853@rasmusvillemoes.dk> (raw)
In-Reply-To: <20181003021358.GA20553@sigill.intra.peff.net>

On 2018-10-03 04:13, Jeff King wrote:
>> +		/*
>> +		 * If we were invoked as "git help cmd", or cmd is an
>> +		 * alias for a shell command, we inform the user what
>> +		 * cmd is an alias for and do nothing else.
>> +		 */
>> +		if (!exclude_guides || alias[0] == '!') {
>> +			printf_ln(_("'%s' is aliased to '%s'"), cmd, alias);
>> +			free(alias);
>> +			exit(0);
>> +		}
> 
> I'm not sure I understand why exclude_guides is relevant. We check it
> below when we know that we _don't_ have an alias. Hrm. I guess you're
> using it here as a proxy for "git foo --help" being used instead of "git
> help foo".

Exactly. Perhaps it's abusing the existing machinery, but I didn't know
how else to distinguish the two cases, and didn't feel like introducing
another way of passing on the exact same information.

> The comment probably needs to spell out that exclude_guides
> is the same as your "we were invoked as...".

Will do. That will also make the string --exclude-guides (i.e., with a
dash) appear in the comment, making it more likely to be found should
anyone change when and how --exclude-guides is implied.

> I wonder if we could change the name of that option. It is an
> undocumented, hidden option that we use internally, so it should be OK
> to do so (or we could always add another one). That might prevent
> somebody in the future from using --exclude-guides in more places and
> breaking your assumption here.

Perhaps, but I think that's better left for a separate patch, if really
necessary even with the expanded comment.

>> +		count = split_cmdline(alias, &argv);
>> +		if (count < 0)
>> +			die(_("bad alias.%s string: %s"), cmd,
>> +			    split_cmdline_strerror(count));
>> +		return alias;
> 
> So we split only to find argv[0] here. But then we don't return it. That
> works because the split is done in place, meaning we must have inserted
> a NUL in alias. That's sufficiently subtle that it might be worth
> spelling it out in a comment.

OK, I actually had precisely

+		/*
+		 * We use split_cmdline() to get the first word of the
+		 * alias, to ensure that we use the same rules as when
+		 * the alias is actually used. split_cmdline()
+		 * modifies alias in-place.
+		 */

in v1, but thought it might be overly verbose. I'll put it back in.

> We don't need to free alias here as we do above, because we're passing
> it back. We should free argv, though, I think (not its elements, just
> the array itself).

Yeah, I thought about this, and removing free(argv) was the last thing I
did before sending v1 - because we were going to leak alias anyway. I'm
happy to put it back in, along with...

> Unfortunately the caller is going to leak our returned "alias", [...] I think it may be OK to overlook
> that and just UNLEAK() it in cmd_help().

...this. Except I'd rather do the UNLEAK in check_git_cmd (the
documentation does say "only from cmd_* functions or their direct
helpers") to make it a more targeted annotation.

Thanks,
Rasmus

  reply	other threads:[~2018-10-03  6:24 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-26 10:26 [PATCH] help: allow redirecting to help for aliased command Rasmus Villemoes
2018-09-26 14:37 ` Taylor Blau
2018-09-26 15:19   ` Duy Nguyen
2018-09-28  7:44     ` Rasmus Villemoes
2018-09-26 15:30   ` Junio C Hamano
2018-09-26 18:09     ` Taylor Blau
2018-09-26 18:20       ` Junio C Hamano
2018-09-26 15:16 ` Duy Nguyen
2018-09-26 15:16 ` Junio C Hamano
2018-09-26 18:12   ` Taylor Blau
2018-09-28  7:53     ` Rasmus Villemoes
2018-09-26 18:49   ` Jeff King
2018-09-26 19:31     ` Junio C Hamano
2018-09-28  8:18     ` Rasmus Villemoes
2018-09-29  8:21       ` Jeff King
2018-09-29 17:39         ` Junio C Hamano
2018-09-30  4:27           ` Jeff King
2018-09-30  5:27             ` Junio C Hamano
2018-09-30  5:53               ` Jeff King
2018-09-28  7:40   ` Rasmus Villemoes
2018-09-28 17:00     ` Junio C Hamano
2018-10-01 11:21 ` [PATCH v2 1/3] help: redirect to aliased commands for "git cmd --help" Rasmus Villemoes
2018-10-01 11:21   ` [PATCH v2 2/3] git.c: handle_alias: prepend alias info when first argument is -h Rasmus Villemoes
2018-10-03  2:16     ` Jeff King
2018-10-01 11:21   ` [PATCH v2 3/3] git-help.txt: document "git help cmd" vs "git cmd --help" for aliases Rasmus Villemoes
2018-10-03  2:18     ` Jeff King
2018-10-03  6:25       ` Rasmus Villemoes
2018-10-03  2:13   ` [PATCH v2 1/3] help: redirect to aliased commands for "git cmd --help" Jeff King
2018-10-03  6:24     ` Rasmus Villemoes [this message]
2018-10-03  7:06       ` Jeff King
2018-10-03 11:42   ` [PATCH v3 0/3] alias help tweaks Rasmus Villemoes
2018-10-03 11:42     ` [PATCH v3 1/3] help: redirect to aliased commands for "git cmd --help" Rasmus Villemoes
2018-10-05  8:19       ` Junio C Hamano
2018-10-05 10:22         ` Rasmus Villemoes
2018-10-05 16:47           ` Junio C Hamano
2018-10-03 11:42     ` [PATCH v3 2/3] git.c: handle_alias: prepend alias info when first argument is -h Rasmus Villemoes
2018-10-03 11:42     ` [PATCH v3 3/3] git-help.txt: document "git help cmd" vs "git cmd --help" for aliases Rasmus Villemoes
2018-10-04  0:10     ` [PATCH v3 0/3] alias help tweaks Jeff King
2018-10-09 11:59     ` [PATCH v4 " Rasmus Villemoes
2018-10-09 11:59       ` [PATCH v4 1/3] help: redirect to aliased commands for "git cmd --help" Rasmus Villemoes
2018-10-09 11:59       ` [PATCH v4 2/3] git.c: handle_alias: prepend alias info when first argument is -h Rasmus Villemoes
2018-10-09 11:59       ` [PATCH v4 3/3] git-help.txt: document "git help cmd" vs "git cmd --help" for aliases Rasmus Villemoes
2018-10-12  3:17       ` [PATCH v4 0/3] alias help tweaks Junio C Hamano

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