Re: Finally implement "git log --follow"

["Marco Costalba" <mcostalba@gmail.com>]

On 6/19/07, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
>  - the commit simplification isn't done. So you cannot do "--follow"
>    together with somethign that wants a contiguous history (like gitk) and
>    uses "--parents".
>
>    This is pretty fundamental. The commit simplification is a separate
>    phase over the (non-linear!) commit space, and the "git log --follow"
>    logic is really a *different* logic over the _linear_ space (namely the
>    streaming "log output" space).
>
>    Two totally different things, in other words. And not compatible.
>

Of course I need exactly that!

Really don't want to thrash away the nice qgit graph, also in file
histories, and at the same time I really like that '--follow' feature,
so....

I've just started to hit the wall against the scary revision.c and
friends, my goal is to find a solution (trick/hack) to get the renames
also with --parents.

First of all I have commented out:

		/* Can't prune commits with rename following: the paths change.. */
// 		if (!revs->diffopt.follow_renames)
			revs->prune_fn = try_to_simplify_commit;

So I've see that with --parents set try_to_simplify_commit() does his
job and when the processing arrives in diff_tree_sha1() it is already
pruned, so also if the check

if (opt->follow_renames && diff_might_be_rename())

is true and the following try_to_follow_renames() is called, no
alternative tree is found.

My idea, after have understood a little bit better how it works, is to
'resurrect' the pruned info  before calling try_to_follow_renames().
To do this I was thinking of saving a pointer to some pruned tree
information in try_to_simplify_commit() and in case use that pointer
after in diff_tree_sha1() when needed.

Nightmares??? Perhaps, I'm just starting with this difficult piece of
code and probably (90%) I will give up before the end and very
probably (99%) all said before is just brain dead, but...anyway I have
to start from somewhere.

Marco