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From: Chris Torek <chris.torek@gmail.com>
To: "brian m. carlson" <sandals@crustytoothpaste.net>,
	Taylor Blau <me@ttaylorr.com>, Denton Liu <liu.denton@gmail.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 2/4] builtin/rev-parse: learn --null-oid
Date: Sat, 19 Sep 2020 21:25:33 -0700	[thread overview]
Message-ID: <CAPx1Gvd6vcvM410wZUZygr4-2Ob6gaScF3DnBtWWsT95XDmKSQ@mail.gmail.com> (raw)
In-Reply-To: <20200918212609.GC67496@camp.crustytoothpaste.net>

On Fri, Sep 18, 2020 at 2:34 PM brian m. carlson
<sandals@crustytoothpaste.net> wrote:
> So I definitely want to distinguish between the null (all-zeros) OID and
> the OID of an empty object, and I think using "null" and "empty" are
> fine.

(I like this myself)

> What I typically do when I write shell scripts, and which may obviate
> the need for this patch is turn this:
>
>   [ "$oid" = 0000000000000000000000000000000000000000 ]
>
> into this:
>
>   echo "$oid" | grep -qsE '^0+$'
>
> This is slightly less efficient, but it's also backwards compatible
> with older Git version assuming you have a POSIX grep.

Note that a lot of `grep`s do not have `-q` and/or `-s` so the
portable variant of this is `grep '^0+$' >/dev/null` (you only need
the `2>&1` part if you're concerned about bad input files or
an error on a pipe or something).

> I'm not sure we need an empty tree and empty blob object, because it's
> pretty easy to write these:
>
>   git hash-object -t tree /dev/null
>   git hash-object -t blob /dev/null
>
> That's what I've done in some of the transition code at least.

That's what's recommended in my 2012 stackoverflow Q&A, too.
The use of `/dev/null` directly here is perhaps unsatisfactory on
old Windows systems, though...?

Chris

  reply	other threads:[~2020-09-20  4:26 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-18 11:19 [PATCH 0/4] sample hooks: become hash agnostic Denton Liu
2020-09-18 11:19 ` [PATCH 1/4] hooks--pre-push.sample: prefer $() for command substitution Denton Liu
2020-09-18 16:57   ` Eric Sunshine
2020-09-18 11:19 ` [PATCH 2/4] builtin/rev-parse: learn --null-oid Denton Liu
2020-09-18 14:11   ` Taylor Blau
2020-09-18 14:16     ` Taylor Blau
2020-09-18 18:16       ` Junio C Hamano
2020-09-18 18:21         ` Taylor Blau
2020-09-18 21:26     ` brian m. carlson
2020-09-20  4:25       ` Chris Torek [this message]
2020-09-20 18:58         ` brian m. carlson
2020-09-20 15:35       ` Taylor Blau
2020-09-20 16:03       ` Andreas Schwab
2020-09-18 11:19 ` [PATCH 3/4] hooks--pre-push.sample: use hash-agnostic null OID Denton Liu
2020-09-18 17:06   ` Eric Sunshine
2020-09-18 11:19 ` [PATCH 4/4] hooks--update.sample: " Denton Liu
2020-09-18 17:08   ` Eric Sunshine
2020-09-18 21:35 ` [PATCH 0/4] sample hooks: become hash agnostic brian m. carlson
2020-09-23  9:38 ` [PATCH v2 0/3] " Denton Liu
2020-09-23  9:38   ` [PATCH v2 1/3] hooks--pre-push.sample: modernize script Denton Liu
2020-09-23  9:38   ` [PATCH v2 2/3] hooks--pre-push.sample: use hash-agnostic zero OID Denton Liu
2020-09-23  9:38   ` [PATCH v2 3/3] hooks--update.sample: " Denton Liu
2020-09-23 16:34   ` [PATCH v2 0/3] sample hooks: become hash agnostic Junio C Hamano

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