Re: Git log follow question

[Jeff King <peff@peff.net>]

On Fri, May 14, 2010 at 10:57:34AM +1000, Albert Krawczyk wrote:

> I'm having an issue understanding the way git log --follow works with git
> log --parents
>
> When I run
> git log --parents --pretty=format:Commit:%H%nParent:%P%n%n alloc.c
> I get:
> Commit:4b25d091ba53c758fae0096b8c0662371857b9d9
> Parent:100c5f3b0b27ec6617de1a785c4ff481e92636c1
>
> [...]
>
> When I try to run git log --parents --follow I get this:
> git log --parents --follow --pretty=format:Commit:%H%nParent:%P%n%n alloc.c
>
> Commit:4b25d091ba53c758fae0096b8c0662371857b9d9
> Parent:75b44066f3ed7cde238cdea1f0bf9e2f1744c820

Hmm. The actual parent is 75b44066. You get 100c5f in the first case
because basic revision path-limiting simplifies the history graph to
remove uninteresting commits (and rewrites the parents).

So the answer isn't _wrong_ exactly, but it is less useful. Seeing the
simplified graph is generally what we want. This is a limitation of the
way --follow is implemented. It turns off history pruning because our
list of what to prune will be changing over time.

Probably we would have to special-case the FOLLOW_RENAMES code to
rewrite the parent list before display.

I'm cc'ing Linus, who has more of a clue in both of those areas than I
do.

-Peff