Re: Suggestion on hashing

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Dec 6, 2011, 06:23 UTC
Message-ID: <CACsJy8CXkz-W3Z3pX-C-+fjLz=WahBajE2uLEG-f3gG_svEhug@mail.gmail.com>
In-Reply-To: <1323151347.1745.73.camel@yos>

On Tue, Dec 6, 2011 at 1:02 PM, Bill Zaumen <bill.zaumen@gmail.com> wrote:

Show 20 quoted lines

> On Tue, 2011-12-06 at 11:46 +0700, Nguyen Thai Ngoc Duy wrote:
>> On Tue, Dec 6, 2011 at 8:56 AM, Chris West (Faux) <faux@goeswhere.com> wrote:
>> >
>> > Nguyen Thai Ngoc Duy wrote:
>> >>
>> >> SHA-1 charateristics (like 20 byte length) are hard coded everywhere
>> >> in git, it'd be a big audit.
>> >
>> >
>> > I was planning to look at this anyway.  My branch[1] allows
>> >  init/add/commit with SHA-256, SHA-512 and all the SHA-3 candidates.
>>
>> Great!
>
> If you are replacing SHA-1 as an object ID with another hash function,
> two things to watch are submodules and alternative object databases.
> Because of those, it is necessary to worry about the order in which
> repositories are converted.  In the worst case for submodules, you'd
> have to do multiple repositories at the same time, switching between
> them depending on what you need at each point.

I know migration would be painful. But note that new repos can benefit stronger digest without legacy (of course until it links to an old repo). For submodules, I think we should extend it to become something similar to soft-link: git link is an SHA-1 to a text file that contains SHA-1 and maybe other digests of the submodule's tip.

-- 
Duy