Re: identifying blobs (was Re: Memory overrun in http-push.c)

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mar 2, 2007, 23:10 UTC
Message-ID: <Pine.LNX.4.64.0703021505380.3953@woody.linux-foundation.org>
In-Reply-To: <7vr6s7dzrh.fsf@assigned-by-dhcp.cox.net>

On Fri, 2 Mar 2007, Junio C Hamano wrote:

Show 9 quoted lines

> 
> It wasn't that identifying the commit that contained the version
> of the file was not needed.  It is just there already is a way
> to do so, and "to create git command" turns out to be
> unnecessary.  Something like:
> 
> 	$ hash=`git hash-object --stdin <$file_in_question`
> 	$ git log -z --raw -r --abbrev=40 |
>           grep -z '^:[0-7][0-7]* [0-7][0-7]* [0-9a-f][0-9a-f]* '"$hash"'

That's not very nice, because if the blob is already in the *top* commit, and isn't changed in a long long time, you'll not see it until it changes (which is potentially at the root commit when it was introduced).

So it's better to do something like

 - get the hash

	hash=`git hash-object --stdin <$file_in_question`

 - see if it is in the current top of the tree

	git ls-tree -r HEAD | cut -d3- | grep ^$hash

 - after that, start doing the backwards searching for things where it 
   went away if it was there before (roughly your "git log -z ...")

which should be fairly simple and straightforward.

For extra bonus points, the script could be trivially written so that it allows the user to specify a path limiter, so that you say "can you tell me which version this blob existed in, but I only want to know about drivers/scsi/ and include/scsi/"

		Linus