The content of this blog is my personal opinion only. Although I am an employee - currently of Imagination Technologies's MIPS group, in the past of other companies such as Intellectual Ventures, Intel, AMD, Motorola, and Gould - I reveal this only so that the reader may account for any possible bias I may have towards my employer's products. The statements I make here in no way represent my employer's position, nor am I authorized to speak on behalf of my employer. In fact, this posting may not even represent my personal opinion, since occasionally I play devil's advocate.

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Saturday, September 02, 2006

Git, Renaming, etc

Git does not track file renames.

Linus's email, http://permalink.gmane.org/gmane.comp.version-control.git/217, is essentially correct, but shortsighted. Linus argues that file renames are just a special case of moving content around. E.g. how does file rename tracking help you if you take a source file foo.h, move all of its content to bar.h, and then put #include "bar.h" inside foo.h? Linus argues that a content based tool that can detect this sort of movement, is more useful than tracking renames in Git.

Linus is right. But, Linus is shortsighted. Linus is considering only one usage model: that of a programmer studying code history. There is a human in the loop.

I want to use a version control system such as Git to perform such actions when a human is not in the loop.

E.g. I want to use Git, instead of RCS, as the version control system in twiki. Then, if a user requests http://mytwikisite.net/OldTopic, I can tell him or her that OldTopic has moved to NewTopic. To do this, the content tracking system must be able to make a single suggestion.

Of course, a content tracking system can make a single suggestion. But, it may get confused - e.g. two different wiki pages may start off from a common answer. Some human may have to decide who is the most logical primary choice. If that choice has been made, why not record it? Which amounts to recording the "primary" renaming.

Similarly, even a wiki may want to have a content tracking system that has a human in the loop. But it is nice to have a fully automated system with no human in the loop, that takes advantage of recorded rename tracking.

And, I hazard, even an SCM will need the fully automated version.


Rename tracking is a convenience.

Content tracking, with or without a human in the loop, is of additional value.

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