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From: Michael Haggerty <mhagger@alum.mit.edu>
To: Brad King <brad.king@kitware.com>
Cc: Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>,
	Vicent Marti <tanoku@gmail.com>,
	Johan Herland <johan@herland.net>,
	git@vger.kernel.org
Subject: Re: [PATCH 03/26] t1400: Pass a legitimate <newvalue> to update command
Date: Mon, 10 Mar 2014 22:38:31 +0100	[thread overview]
Message-ID: <531E30D7.40208@alum.mit.edu> (raw)
In-Reply-To: <531DF079.9050909@kitware.com>

Brad,

Thanks for your feedback.

On 03/10/2014 06:03 PM, Brad King wrote:
> On 03/10/2014 08:46 AM, Michael Haggerty wrote:
>> This test is trying to test a few ways to delete references using "git
>> update-ref -z --stdin".  The third line passed in is
>>
>>     update SP /refs/heads/c NUL NUL <sha1> NUL
>>
>> , which is not a correct way to delete a reference according to the
>> documentation (the new value should be zeros, not empty).  Pass zeros
>> instead as the new value to test the code correctly.
> 
> In my original work on this feature, an empty <newvalue> is allowed.
> Since newvalue is not optional an empty value can be treated as zero.
> The relevant documentation is:
> 
>  update::
>          Set <ref> to <newvalue> after verifying <oldvalue>, if given.
>          Specify a zero <newvalue> to ensure the ref does not exist
> 
>  ...
> 
>  Use 40 "0" or the empty string to specify a zero value, except that
>  with `-z` an empty <oldvalue> is considered missing.
> 
> The two together say that <newvalue> can be the empty string instead
> of a literal zero.

OK, with your explanation and after reading the docs a couple more
times, I can see your reading.  Your rules as I now understand them:

* Without -z
  * 0{40} or the empty string represents zeros
  * No preceding SP delimiter indicates that the value is missing
    (as are any following values)

* With -z
  * For <newvalue>
    * 0{40} or the empty string represents zeros (the value is
      not allowed to be missing)
  * For <oldvalue>
    * 0{40} represents zeros
    * The empty string indicates that the value is missing

I implemented the slightly simpler rules

* Without -z
  * 0{40} or the empty string represents zeros
  * No preceding delimiter indicates that the value is missing (as
    are any following values)

* With -z
  * 0{40} represents zeros
  * The empty string indicates that the value is missing

It seems to me that "-z" input will nearly always be machine-generated,
so there is not much reason to accept the empty string as shorthand for
zeros.  So I think that my version of the rules, being simpler to
explain, is a slight improvement.  But your version is already out in
the wild, so backwards-compatibility is also a consideration, even
though it is rather a fine point in a rather unlikely usage (why use
update rather than delete to delete a reference?).

I don't know.  I'm willing to rewrite the code to go back to your rules,
or rewrite the documentation to describe my rules.

Neutral bystanders *cough*Junio*cough*, what do you prefer?

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/

  reply	other threads:[~2014-03-10 21:38 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-10 12:46 [PATCH 00/26] Clean up update-refs --stdin and implement ref_transaction Michael Haggerty
2014-03-10 12:46 ` [PATCH 01/26] t1400: Fix name and expected result of one test Michael Haggerty
2014-03-10 12:46 ` [PATCH 02/26] t1400: Provide sensible input to the command Michael Haggerty
2014-03-10 12:46 ` [PATCH 03/26] t1400: Pass a legitimate <newvalue> to update command Michael Haggerty
2014-03-10 17:03   ` Brad King
2014-03-10 21:38     ` Michael Haggerty [this message]
2014-03-11 12:49       ` Brad King
2014-03-11 20:06       ` Junio C Hamano
2014-03-11 21:41         ` Brad King
2014-03-20 17:01           ` Michael Haggerty
2014-03-10 12:46 ` [PATCH 04/26] parse_arg(): Really test that argument is properly terminated Michael Haggerty
2014-03-10 12:46 ` [PATCH 05/26] t1400: Add some more tests involving quoted arguments Michael Haggerty
2014-03-10 13:53   ` Johan Herland
2014-03-10 12:46 ` [PATCH 06/26] refs.h: Rename the action_on_err constants Michael Haggerty
2014-03-10 12:46 ` [PATCH 07/26] update_refs(): Fix constness Michael Haggerty
2014-03-10 12:46 ` [PATCH 08/26] update-ref --stdin: Read the whole input at once Michael Haggerty
2014-03-10 12:46 ` [PATCH 09/26] parse_cmd_verify(): Copy old_sha1 instead of evaluating <oldvalue> twice Michael Haggerty
2014-03-10 12:46 ` [PATCH 10/26] update-ref.c: Extract a new function, parse_refname() Michael Haggerty
2014-03-10 12:46 ` [PATCH 11/26] update-ref --stdin: Improve error messages for invalid values Michael Haggerty
2014-03-10 12:46 ` [PATCH 12/26] update-ref --stdin: Make error messages more consistent Michael Haggerty
2014-03-10 12:46 ` [PATCH 13/26] update-ref --stdin: Simplify error messages for missing oldvalues Michael Haggerty
2014-03-10 17:08   ` Brad King
2014-03-10 17:12     ` Brad King
2014-03-10 12:46 ` [PATCH 14/26] update-ref.c: Extract a new function, parse_next_sha1() Michael Haggerty
2014-03-10 12:46 ` [PATCH 15/26] update-ref --stdin: Improve the error message for unexpected EOF Michael Haggerty
2014-03-10 12:46 ` [PATCH 16/26] update-ref --stdin: Harmonize error messages Michael Haggerty
2014-03-10 12:46 ` [PATCH 17/26] refs: Add a concept of a reference transaction Michael Haggerty
2014-03-10 12:46 ` [PATCH 18/26] update-ref --stdin: Reimplement using reference transactions Michael Haggerty
2014-03-10 12:46 ` [PATCH 19/26] refs: Remove API function update_refs() Michael Haggerty
2014-03-10 12:46 ` [PATCH 20/26] struct ref_update: Rename field "ref_name" to "refname" Michael Haggerty
2014-03-10 12:46 ` [PATCH 21/26] struct ref_update: Store refname as a FLEX_ARRAY Michael Haggerty
2014-03-10 12:46 ` [PATCH 22/26] commit_ref_transaction(): Introduce temporary variables Michael Haggerty
2014-03-10 12:46 ` [PATCH 23/26] struct ref_update: Add a lock member Michael Haggerty
2014-03-10 12:46 ` [PATCH 24/26] struct ref_update: Add type field Michael Haggerty
2014-03-10 12:46 ` [PATCH 25/26] commit_ref_transaction(): Also free the ref_transaction Michael Haggerty
2014-03-10 12:46 ` [PATCH 26/26] commit_ref_transaction(): Work with transaction->updates in place Michael Haggerty
2014-03-10 17:44 ` [PATCH 00/26] Clean up update-refs --stdin and implement ref_transaction Brad King
2014-03-10 21:46   ` Michael Haggerty

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