Re: git-mv redux: there must be something else going on

From: Nicolas Pitre <nico@fluxnic.net>
Date: Feb 3, 2010, 19:53 UTC
Message-ID: <alpine.LFD.2.00.1002031436490.1681@xanadu.home>
In-Reply-To: <ron1-5F71CB.11234903022010@news.gmane.org>

On Wed, 3 Feb 2010, Ron Garret wrote:

Show 5 quoted lines

> So... how *does* git decide when two blobs are different blobs and when 
> they are the same blob with mods?  I asked this question before and was 
> pointed to the diffcore docs, but that didn't really clear things up.  
> That just describes all the different ways git can do diffs, not the 
> actual heuristics that git uses to track content.

Yes, those same heuristics are used to make the decision.

|The second transformation in the chain is diffcore-break, and is
|controlled by the -B option to the 'git diff-{asterisk}' commands.  
|This is used to detect a filepair that represents "complete rewrite" 
|and break such filepair into two filepairs that represent delete and
|create.
|[...]

|This transformation is used to detect renames and copies, and is
|controlled by the -M option (to detect renames) and the -C option
|(to detect copies as well) to the 'git diff-{asterisk}' commands.  
|[...]

Note that you may use the -B, -C, -M and --find-copies-harder arguments with log as well as diff commands even if there is no actual diff output. So the explanation is really in that document even if simple rename detection is concerned only by a fraction of what is said there.

And Git can detect copied files too.

Those semantics are not stored in the repository so they can be improved or even changed after the facts.

Nicolas