Re: [RFC/WIP] Pluggable reference backends

[David Lang <david@lang.hm>]

On Mon, 10 Mar 2014, David Kastrup wrote:

> Jeff King <peff@peff.net> writes:
>
>> On Mon, Mar 10, 2014 at 07:30:45AM -0700, Shawn Pearce wrote:
>>
>>>> * Store references in a SQLite database, to get correct transaction
>>>>   handling.
>>>
>>> No to SQLLite in git-core. Using it from JGit requires building
>>> SQLLite and a JNI wrapper, which makes JGit significantly less
>>> portable. I know SQLLite is pretty amazing, but implementing
>>> compatibility with it from JGit will be a big nightmare for us.
>>
>> That seems like a poor reason not to implement a pluggable feature for
>> git-core. If we implement it, then a site using only git-core can take
>> advantage of it. Sites with JGit cannot, and would use a different
>> pluggable storage mechanism that's supported by both. But if we don't
>> implement, it hurts people using only git-core, and it does not help
>> sites using JGit at all.
>
> Of course, the basic premise for this feature is "let's assume that our
> file and/or operating system suck at providing file system functionality
> at file name granularity".  There have been two historically approaches
> to that problem that are not independent: a) use Linux b) kick Linus.

As a note, if this is done properly, it could allow for plugins that connect to 
the underlying storage system (similar to the Facebook Mecurial change)

Even for those who don't have the $$$$$ storage arrays, there may be other 
storage specific hacks that can be done to detect that files haven't changed.

For example, with btrfs and you compile into a different directory thatn your 
source, you may be able to detect that things didn't change by the fact that the 
filesystem didn't have to do a rewrite of the parent node.

David Lang