From: Todd Zullinger <tmz@pobox.com>
Date: Wed, 23 May 2018 22:19:02 GMT
Subject: Re: [PATCH 2/2] rev-parse: verify that commit looked up is not NULL
Message-ID: <20180523221901.GV26695@zaya.teonanacatl.net>
In-Reply-To: <20180523204613.11333-2-newren@gmail.com>

Elijah Newren wrote:
> In commit 2122f8b963d4 ("rev-parse: Add support for the ^! and ^@ syntax",
> 2008-07-26), try_parent_shorthands() was introduced to parse the special
> ^! and ^@ syntax.  However, it did not check the commit returned from
> lookup_commit_reference() before proceeding to use it.  If it is NULL,
> bail early and notify the caller that this cannot be a valid revision
> range.

Thanks.  This fixes the segfault.  While I was testing this,
I wondered if the following cases should differ:

#          f*40
$ ./git-rev-parse ffffffffffffffffffffffffffffffffffffffff^@ ; echo $?
0

#          f*39
$ ./git-rev-parse fffffffffffffffffffffffffffffffffffffff^@ ; echo $?
fffffffffffffffffffffffffffffffffffffff^@
fatal: ambiguous argument 'fffffffffffffffffffffffffffffffffffffff^@': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'
128

Looking a little further, this is deeper than the rev-parse
handling.  The difference in how these invalid refs are
handled appears in 'git show' as well.  With 'git show' a
(different) fatal error is returned in both cases.

#          f*40
$ git show ffffffffffffffffffffffffffffffffffffffff
fatal: bad object ffffffffffffffffffffffffffffffffffffffff

#          39*f
$ git show fffffffffffffffffffffffffffffffffffffff
fatal: ambiguous argument 'fffffffffffffffffffffffffffffffffffffff': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

Should rev-parse return an error as well, rather than
silenty succeeding?

-- 
Todd
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I refuse to spend my life worrying about what I eat. There is no
pleasure worth foregoing just for an extra three years in the
geriatric ward.
    -- John Mortimer