Re: [PATCH 2/2] Support "history replay" for git log commands

[Junio C Hamano <gitster@pobox.com>]

Linus Torvalds <torvalds@linux-foundation.org> writes:

> This notices if we aren't in topological order, and replays the history. 
> Thus avoiding the need to sort history up front.
>     
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
>
> See the code and the more complete explanations in [PATCH 0/2]. In 
> particular, see the last section there about the downsides of this: the 
> 50x expansion of output on the kernel is unacceptable, but if somebody can 
> make a graphical viewer that can react correctly to the "Replay" thing, 
> I'm sure I can make the replays themselves happen much more rarely.
>
>  builtin-blame.c |    2 +-
>  builtin-log.c   |   35 +++++++++++++++++++++++++++++++++++
>  log-tree.c      |   10 +++++++---
>  revision.c      |   29 ++++++++++++++++++++++-------
>  revision.h      |    6 +++++-
>  5 files changed, 70 insertions(+), 12 deletions(-)
>
> diff --git a/builtin-blame.c b/builtin-blame.c
> index 8432b82..7b6af8c 100644
> --- a/builtin-blame.c
> +++ b/builtin-blame.c
> @@ -1502,7 +1502,7 @@ static void assign_blame(struct scoreboard *sb, struct rev_info *revs, int opt)
>  		else {
>  			commit->object.flags |= UNINTERESTING;
>  			if (commit->object.parsed)
> -				mark_parents_uninteresting(commit);
> +				mark_parents_uninteresting(revs, commit);
>  		}
>  		/* treat root commit as boundary */
>  		if (!commit->parents && !show_root)
> diff --git a/builtin-log.c b/builtin-log.c
> index e8b982d..10e0821 100644
> --- a/builtin-log.c
> +++ b/builtin-log.c
> @@ -77,6 +77,35 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
>  	}
>  }
>  
> +static void replay_history(struct rev_info *revs)
> +{
> +	struct commit_list *entry;
> +
> +	revs->trigger_replay = 0;
> +	while ((entry = revs->shown) != NULL) {
> +		struct commit *commit = entry->item;
> +		unsigned flags = commit->object.flags;
> +
> +		/* Undo the SHOWN and FORCE_REPLAY bits */
> +		commit->object.flags = flags & ~(SHOWN | FORCE_REPLAY);
> +		commit->indegree = 0;
> +
> +		/* Remove it from the shown list, put it on the commit list */
> +		revs->shown = entry->next;
> +		entry->next = revs->commits;
> +		revs->commits = entry;
> +
> +		printf("Replay %s\n", sha1_to_hex(commit->object.sha1));
> +
> +		/* Was this the one that caused us to replay? */
> +		if (flags & FORCE_REPLAY)
> +			break;

Can one iteration of loop in log_tree_commit() smudge more
than one commits with FORCE_REPLAY?  Maybe make the
trigger_replay a counter and count down in this loop until we
find that many commits that have the FORCE_REPLAY flag?