Re: Re: [PATCH v5 1/3] Teach revision walking machinery to walk multiple times sequencially

[Heiko Voigt <hvoigt@hvoigt.net>]

Hi,

sorry that my reply to this took quite some time.

On Mon, Feb 13, 2012 at 05:33:34PM -0800, Junio C Hamano wrote:
> Heiko Voigt <hvoigt@hvoigt.net> writes:
> 
> > Previously it was not possible to iterate revisions twice using the
> > revision walking api. We add a reset_revision_walk() which clears the
> > used flags. This allows us to do multiple sequencial revision walks.
> >
> > Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
> 
> I am kind of surprised that this is already its 5th round.

Well, not this patch in particular but the series so I chose to it for
the whole series.

> Minimally,
> 
>         void clear_object_flags(unsigned flags)
>         {
>                 int i;
> 
>                 for (i = 0; i < obj_hash_size; i++) {
>                         struct object *obj = obj_hash[i];
>                         if (obj && (obj->flags & flags))
>                                 obj->flags &= ~flags;
>                 }
>         }
> 
> I am not sure if the "If there is any bit set we care about, drop them"
> buys us anything, though.

Ok done. And also dropped the "if there is any bit set" condition.

> > +void reset_revision_walk()
> 
> 	void reset_revision_walk(void)

Done.

> > +{
> > +	clear_object_flags(SEEN | ADDED | SHOWN);
> > +}
> 
> But is this really the right API?  After a particular program finishes
> using the revision walker, wouldn't it want to clear both the set of these
> standard flag bits used by the traversal machinery, as well as whatever
> program specific bits it used to mark the objects with?

Well if a program uses extra flags on objects it should clear the flags
it set by using the clear_objects_flags() function itself. For example if
the program wants to reuse those extra flags in a second revision walk
it would not be possible if reset_revision_walk() would clear all flags.

> > diff --git a/revision.h b/revision.h
> > index b8e9223..3535733 100644
> > --- a/revision.h
> > +++ b/revision.h
> > @@ -192,6 +192,7 @@ extern void parse_revision_opt(struct rev_info *revs, struct parse_opt_ctx_t *ct
> >  ...
> > +extern void reset_revision_walk();
> 
> Likewise, "extern void reset_revision_walk(void);".

Done.

> 
> > diff --git a/submodule.c b/submodule.c
> > index 9a28060..645ff5d 100644
> > --- a/submodule.c
> > +++ b/submodule.c
> > @@ -404,6 +404,7 @@ int check_submodule_needs_pushing(unsigned char new_sha1[20], const char *remote
> >  	while ((commit = get_revision(&rev)) && !needs_pushing)
> >  		commit_need_pushing(commit, &needs_pushing);
> >  
> > +	reset_revision_walk();
> >  	free(sha1_copy);
> >  	strbuf_release(&remotes_arg);
> >  
> > @@ -741,6 +742,7 @@ static int find_first_merges(struct object_array *result, const char *path,
> >  		if (in_merge_bases(b, &commit, 1))
> >  			add_object_array(o, NULL, &merges);
> >  	}
> > +	reset_revision_walk();
> >  
> >  	/* Now we've got all merges that contain a and b. Prune all
> >  	 * merges that contain another found merge and save them in
> 
> These two hunk look like a *BUGFIX* to me (certainly it does not look like
> this is an addition of any new feature).
> 
> What bug does this fix, and how is the current submodule code broken
> without this patch?  Can you describe the problem in the log message, and
> add a test to demonstrate the existing breakage?

There is no breakage I know of. Its rather a cleanup which allows to
call these functions multiple times. I did this to avoid surprises.
Should I put these in a separate patch or just add an explanation into
the current one?

Cheers Heiko