Re: [PATCH v6] Implement --first-parent for git rev-list --bisect

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Tiago,

On Tue, 28 Aug 2018, Tiago Botelho wrote:

> This will enable users to implement bisecting on first parents
> which can be useful for when the commits from a feature branch
> that we want to merge are not always tested.

This message is still lacking the explanation I asked for, namely for the
lines:

	@@ -329,6 +334,11 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
	 	if (0 <= weight(p))
	 		continue;
	 	for (q = p->item->parents; q; q = q->next) {
	+		if ((bisect_flags & BISECT_FIRST_PARENT)) {
	+			if (weight(q) < 0)
	+				q = NULL;
	+			break;
	+		}
	 	if (q->item->object.flags & UNINTERESTING)
	 		continue;
	 	if (0 <= weight(q))

> Signed-off-by: Tiago Botelho <tiagonbotelho@hotmail.com>
> ---
> 
> This patch refactors **only** the tests according to the suggestions made by Junio in v5
> more specifically `https://public-inbox.org/git/xmqqa7rhi40f.fsf@gitster-ct.c.googlers.com/`.
> 
> The discussion between Junio, Christian and Johannes got pretty confusing in the sense
> that I am unsure if this is the actual problem I am supposed to solve in order to get the
> patch accepted, if it is not I will keep iterating on it until it is good enough to be
> merged

I would have preferred to reuse the already existing commits generated in
the `setup` phase rather than generating yet another batch, and to not
introduce an inconsistent way to present a commit graph (compare your
diagram with the one in
https://github.com/git/git/blob/v2.18.0/t/t6002-rev-list-bisect.sh#L64-L90
i.e. *in the same file*), and I mentioned this at least twice before, but
maybe it got lost (and I could imagine that Christian's insistence on
pushing the patch through with as little changes as he can get away with
does not help), but at least now the added tests look slightly more
understandable than before (despite funny indentation and too-long lines),
so I'll stop imitating a broken record at this point.

Ciao,
Johannes

> 
>  bisect.c                   | 43 ++++++++++++++++++++++------------
>  bisect.h                   |  1 +
>  builtin/rev-list.c         |  3 +++
>  revision.c                 |  3 ---
>  t/t6002-rev-list-bisect.sh | 58 ++++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 90 insertions(+), 18 deletions(-)
> 
> diff --git a/bisect.c b/bisect.c
> index 4eafc8262..cb80f29c5 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -82,15 +82,16 @@ static inline void weight_set(struct commit_list *elem, int weight)
>  	*((int*)(elem->item->util)) = weight;
>  }
>  
> -static int count_interesting_parents(struct commit *commit)
> +static int count_interesting_parents(struct commit *commit, unsigned bisect_flags)
>  {
>  	struct commit_list *p;
>  	int count;
>  
>  	for (count = 0, p = commit->parents; p; p = p->next) {
> -		if (p->item->object.flags & UNINTERESTING)
> -			continue;
> -		count++;
> +		if (!(p->item->object.flags & UNINTERESTING))
> +		    count++;
> +		if (bisect_flags & BISECT_FIRST_PARENT)
> +			break;
>  	}
>  	return count;
>  }
> @@ -117,10 +118,10 @@ static inline int halfway(struct commit_list *p, int nr)
>  }
>  
>  #if !DEBUG_BISECT
> -#define show_list(a,b,c,d) do { ; } while (0)
> +#define show_list(a,b,c,d,e) do { ; } while (0)
>  #else
>  static void show_list(const char *debug, int counted, int nr,
> -		      struct commit_list *list)
> +		      struct commit_list *list, unsigned bisect_flags)
>  {
>  	struct commit_list *p;
>  
> @@ -146,10 +147,14 @@ static void show_list(const char *debug, int counted, int nr,
>  		else
>  			fprintf(stderr, "---");
>  		fprintf(stderr, " %.*s", 8, oid_to_hex(&commit->object.oid));
> -		for (pp = commit->parents; pp; pp = pp->next)
> +		for (pp = commit->parents; pp; pp = pp->next) {
>  			fprintf(stderr, " %.*s", 8,
>  				oid_to_hex(&pp->item->object.oid));
>  
> +			if (bisect_flags & BISECT_FIRST_PARENT)
> +				break;
> +		}
> +
>  		subject_len = find_commit_subject(buf, &subject_start);
>  		if (subject_len)
>  			fprintf(stderr, " %.*s", subject_len, subject_start);
> @@ -267,13 +272,13 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
>  		unsigned flags = commit->object.flags;
>  
>  		p->item->util = &weights[n++];
> -		switch (count_interesting_parents(commit)) {
> +		switch (count_interesting_parents(commit, bisect_flags)) {
>  		case 0:
>  			if (!(flags & TREESAME)) {
>  				weight_set(p, 1);
>  				counted++;
>  				show_list("bisection 2 count one",
> -					  counted, nr, list);
> +					  counted, nr, list, bisect_flags);
>  			}
>  			/*
>  			 * otherwise, it is known not to reach any
> @@ -289,7 +294,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
>  		}
>  	}
>  
> -	show_list("bisection 2 initialize", counted, nr, list);
> +	show_list("bisection 2 initialize", counted, nr, list, bisect_flags);
>  
>  	/*
>  	 * If you have only one parent in the resulting set
> @@ -319,7 +324,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
>  		counted++;
>  	}
>  
> -	show_list("bisection 2 count_distance", counted, nr, list);
> +	show_list("bisection 2 count_distance", counted, nr, list, bisect_flags);
>  
>  	while (counted < nr) {
>  		for (p = list; p; p = p->next) {
> @@ -329,6 +334,11 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
>  			if (0 <= weight(p))
>  				continue;
>  			for (q = p->item->parents; q; q = q->next) {
> +				if ((bisect_flags & BISECT_FIRST_PARENT)) {
> +					if (weight(q) < 0)
> +						q = NULL;
> +					break;
> +				}
>  				if (q->item->object.flags & UNINTERESTING)
>  					continue;
>  				if (0 <= weight(q))
> @@ -346,7 +356,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
>  				weight_set(p, weight(q)+1);
>  				counted++;
>  				show_list("bisection 2 count one",
> -					  counted, nr, list);
> +					  counted, nr, list, bisect_flags);
>  			}
>  			else
>  				weight_set(p, weight(q));
> @@ -357,7 +367,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
>  		}
>  	}
>  
> -	show_list("bisection 2 counted all", counted, nr, list);
> +	show_list("bisection 2 counted all", counted, nr, list, bisect_flags);
>  
>  	if (!find_all)
>  		return best_bisection(list, nr);
> @@ -372,7 +382,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
>  	struct commit_list *list, *p, *best, *next, *last;
>  	int *weights;
>  
> -	show_list("bisection 2 entry", 0, 0, *commit_list);
> +	show_list("bisection 2 entry", 0, 0, *commit_list, bisect_flags);
>  
>  	/*
>  	 * Count the number of total and tree-changing items on the
> @@ -395,7 +405,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
>  		on_list++;
>  	}
>  	list = last;
> -	show_list("bisection 2 sorted", 0, nr, list);
> +	show_list("bisection 2 sorted", 0, nr, list, bisect_flags);
>  
>  	*all = nr;
>  	weights = xcalloc(on_list, sizeof(*weights));
> @@ -962,6 +972,9 @@ int bisect_next_all(const char *prefix, int no_checkout)
>  	if (skipped_revs.nr)
>  		bisect_flags |= BISECT_FIND_ALL;
>  
> +	if (revs.first_parent_only)
> +		bisect_flags |= BISECT_FIRST_PARENT;
> +
>  	find_bisection(&revs.commits, &reaches, &all, bisect_flags);
>  	revs.commits = managed_skipped(revs.commits, &tried);
>  
> diff --git a/bisect.h b/bisect.h
> index 1d40a33ad..e445567c2 100644
> --- a/bisect.h
> +++ b/bisect.h
> @@ -2,6 +2,7 @@
>  #define BISECT_H
>  
>  #define BISECT_FIND_ALL		(1u<<0)
> +#define BISECT_FIRST_PARENT    	(1u<<1)
>  
>  /*
>   * Find bisection. If something is found, `reaches` will be the number of
> diff --git a/builtin/rev-list.c b/builtin/rev-list.c
> index 8752f5bbe..66439e1b3 100644
> --- a/builtin/rev-list.c
> +++ b/builtin/rev-list.c
> @@ -538,6 +538,9 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
>  	if (bisect_list) {
>  		int reaches, all;
>  
> +		if (revs.first_parent_only)
> +			bisect_flags |= BISECT_FIRST_PARENT;
> +
>  		find_bisection(&revs.commits, &reaches, &all, bisect_flags);
>  
>  		if (bisect_show_vars)
> diff --git a/revision.c b/revision.c
> index 4e0e193e5..b9d063805 100644
> --- a/revision.c
> +++ b/revision.c
> @@ -2474,9 +2474,6 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
>  	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
>  		die("cannot use --grep-reflog without --walk-reflogs");
>  
> -	if (revs->first_parent_only && revs->bisect)
> -		die(_("--first-parent is incompatible with --bisect"));
> -
>  	if (revs->expand_tabs_in_log < 0)
>  		revs->expand_tabs_in_log = revs->expand_tabs_in_log_default;
>  
> diff --git a/t/t6002-rev-list-bisect.sh b/t/t6002-rev-list-bisect.sh
> index a66140803..1bc297de5 100755
> --- a/t/t6002-rev-list-bisect.sh
> +++ b/t/t6002-rev-list-bisect.sh
> @@ -263,4 +263,62 @@ test_expect_success 'rev-parse --bisect can default to good/bad refs' '
>  	test_cmp expect.sorted actual.sorted
>  '
>  
> +# We generate the following commit graph:
> +#
> +#   B ------ C
> +#  /          \
> +# A            FX
> +#  \          /
> +#   D - CC - EX
> +
> +test_expect_success 'setup' '
> +  test_commit A &&
> +  test_commit B &&
> +  test_commit C &&
> +  git reset --hard A &&
> +  test_commit D &&
> +  test_commit CC &&
> +  test_commit EX &&
> +  test_merge FX C
> +'
> +
> +test_output_expect_success "--bisect --first-parent" 'git rev-list --bisect --first-parent FX ^A' <<EOF
> +$(git rev-parse CC)
> +EOF
> +
> +test_output_expect_success "--first-parent" 'git rev-list --first-parent FX ^A' <<EOF
> +$(git rev-parse FX)
> +$(git rev-parse EX)
> +$(git rev-parse CC)
> +$(git rev-parse D)
> +EOF
> +
> +test_output_expect_success "--bisect-vars --first-parent" 'git rev-list --bisect-vars --first-parent FX ^A' <<EOF
> +bisect_rev='$(git rev-parse CC)'
> +bisect_nr=1
> +bisect_good=1
> +bisect_bad=1
> +bisect_all=4
> +bisect_steps=1
> +EOF
> +
> +test_expect_success "--bisect-all --first-parent" '
> +cat >expect <<EOF &&
> +$(git rev-parse CC) (dist=2)
> +$(git rev-parse EX) (dist=1)
> +$(git rev-parse D) (dist=1)
> +$(git rev-parse FX) (dist=0)
> +EOF
> +
> +# Make sure we have the same entries, nothing more, nothing less
> +git rev-list --bisect-all --first-parent FX ^A >actual &&
> +  sort actual >actual.sorted &&
> +  sort expect >expect.sorted &&
> +  test_cmp expect.sorted actual.sorted &&
> +  # Make sure the entries are sorted in the dist order
> +  sed -e "s/.*(dist=\([1-9]*[0-9]\)).*/\1/" actual >actual.dists &&
> +  sort -r actual.dists >actual.dists.sorted &&
> +  test_cmp actual.dists.sorted actual.dists
> +'
> +
>  test_done
> -- 
> 2.16.3
> 
>