[RFC PATCH v4] Implement --first-parent for git rev-list --bisect

[RFC PATCH v4] Implement --first-parent for git rev-list --bisect

[Tiago Botelho]

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.

Signed-off-by: Tiago Botelho <tiagonbotelho@hotmail.com>
---

This patch adds all Junio's suggestions, namely do_find_bisection() being
broken when assigning q's weight to p if in first parent mode and q being
not UNINTERESTING and its weight still not being known.

The graph displayed in the unit tests was also changed from being top-bottom
to be left-right in order to keep it consistent with graphs in other tests.

 bisect.c                   | 45 ++++++++++++++++++++++++++++++---------------
 bisect.h                   |  3 ++-
 builtin/rev-list.c         |  3 +++
 revision.c                 |  3 ---
 t/t6002-rev-list-bisect.sh | 37 +++++++++++++++++++++++++++++++++++++
 5 files changed, 72 insertions(+), 19 deletions(-)

diff --git a/bisect.c b/bisect.c
index 4eafc8262..e58cb8d62 100644
--- a/bisect.c
+++ b/bisect.c
@@ -33,6 +33,8 @@ static const char *term_good;
  *
  * We care just barely enough to avoid recursing for
  * non-merge entries.
+ *
+ * Note: This function does not support the usage --first-parent.
  */
 static int count_distance(struct commit_list *entry)
 {
@@ -82,15 +84,16 @@ 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 +120,10 @@ 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 +149,14 @@ 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 +274,13 @@ 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 +296,7 @@ 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 +326,7 @@ 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 +336,11 @@ 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 +358,7 @@ 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 +369,7 @@ 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 +384,7 @@ 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 +407,7 @@ 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 +974,9 @@ 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..dfb7faeec 100644
--- a/bisect.h
+++ b/bisect.h
@@ -1,7 +1,8 @@
 #ifndef BISECT_H
 #define BISECT_H
 
-#define BISECT_FIND_ALL		(1u<<0)
+#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..774d9a4fd 100755
--- a/t/t6002-rev-list-bisect.sh
+++ b/t/t6002-rev-list-bisect.sh
@@ -263,4 +263,41 @@ 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 - EX
+
+test_expect_success 'setup' '
+  test_commit A &&
+  test_commit B &&
+  test_commit C &&
+  git reset --hard A &&
+  test_commit D &&
+  test_commit EX &&
+  test_merge FX C
+'
+
+test_output_expect_success "--bisect --first-parent" 'git rev-list --bisect --first-parent FX ^A' <<EOF
+$(git rev-parse EX)
+EOF
+
+test_output_expect_success "--bisect-vars --first-parent" 'git rev-list --bisect-vars --first-parent FX ^A' <<EOF
+bisect_rev='$(git rev-parse EX)'
+bisect_nr=1
+bisect_good=0
+bisect_bad=1
+bisect_all=3
+bisect_steps=1
+EOF
+
+test_output_expect_success "--bisect-all --first-parent" 'git rev-list --bisect-all --first-parent FX ^A' <<EOF
+$(git rev-parse EX) (dist=1)
+$(git rev-parse D) (dist=1)
+$(git rev-parse FX) (dist=0)
+EOF
+
 test_done
-- 
2.16.3

Re: [RFC PATCH v4] Implement --first-parent for git rev-list --bisect

[Junio C Hamano]

Tiago Botelho <tiagonbotelho@gmail.com> writes:

> diff --git a/bisect.c b/bisect.c
> index 4eafc8262..e58cb8d62 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -33,6 +33,8 @@ static const char *term_good;
>   *
>   * We care just barely enough to avoid recursing for
>   * non-merge entries.
> + *
> + * Note: This function does not support the usage --first-parent.
>   */

Hmph, is this because we know --first-parent codepath currently does
not call this function, so we do not bother to prepare this function
to be called from --first-parent codepath?

I am not saying that we must prepare this function to be callable
with --first-parent; if I have to wonder why the above comment is
there and what it is trying to say, I suspect most other readers
would, too, so...

> diff --git a/t/t6002-rev-list-bisect.sh b/t/t6002-rev-list-bisect.sh
> index a66140803..774d9a4fd 100755
> --- a/t/t6002-rev-list-bisect.sh
> +++ b/t/t6002-rev-list-bisect.sh
> @@ -263,4 +263,41 @@ 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 - EX
> +
> +test_expect_success 'setup' '
> +  test_commit A &&
> +  test_commit B &&
> +  test_commit C &&
> +  git reset --hard A &&
> +  test_commit D &&
> +  test_commit EX &&
> +  test_merge FX C
> +'
> +
> +test_output_expect_success "--bisect --first-parent" 'git rev-list --bisect --first-parent FX ^A' <<EOF
> +$(git rev-parse EX)
> +EOF
> +
> +test_output_expect_success "--bisect-vars --first-parent" 'git rev-list --bisect-vars --first-parent FX ^A' <<EOF
> +bisect_rev='$(git rev-parse EX)'
> +bisect_nr=1
> +bisect_good=0
> +bisect_bad=1
> +bisect_all=3
> +bisect_steps=1
> +EOF
> +
> +test_output_expect_success "--bisect-all --first-parent" 'git rev-list --bisect-all --first-parent FX ^A' <<EOF
> +$(git rev-parse EX) (dist=1)
> +$(git rev-parse D) (dist=1)
> +$(git rev-parse FX) (dist=0)
> +EOF
> +

These are all good basic tests, but can you come up with a test that
demonstrates breakage in the previous round that has been fixed in
this version of the patch?

Thanks.

Re: [RFC PATCH v4] Implement --first-parent for git rev-list --bisect

[Junio C Hamano]

Tiago Botelho <tiagonbotelho@gmail.com> writes:

> 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.
>
> Signed-off-by: Tiago Botelho <tiagonbotelho@hotmail.com>
> ---
>
> This patch adds all Junio's suggestions, namely do_find_bisection() being
> broken when assigning q's weight to p if in first parent mode and q being
> not UNINTERESTING and its weight still not being known.
>
> The graph displayed in the unit tests was also changed from being top-bottom
> to be left-right in order to keep it consistent with graphs in other tests.
>
>  bisect.c                   | 45 ++++++++++++++++++++++++++++++---------------
>  bisect.h                   |  3 ++-
>  builtin/rev-list.c         |  3 +++
>  revision.c                 |  3 ---
>  t/t6002-rev-list-bisect.sh | 37 +++++++++++++++++++++++++++++++++++++
>  5 files changed, 72 insertions(+), 19 deletions(-)

> diff --git a/t/t6002-rev-list-bisect.sh b/t/t6002-rev-list-bisect.sh
> index a66140803..774d9a4fd 100755
> --- a/t/t6002-rev-list-bisect.sh
> +++ b/t/t6002-rev-list-bisect.sh
> @@ -263,4 +263,41 @@ test_expect_success 'rev-parse --bisect can default to good/bad refs' '
> ...
> +test_output_expect_success "--bisect-all --first-parent" 'git rev-list --bisect-all --first-parent FX ^A' <<EOF
> +$(git rev-parse EX) (dist=1)
> +$(git rev-parse D) (dist=1)
> +$(git rev-parse FX) (dist=0)
> +EOF
> +
>  test_done

Running this test number of times gives me spurious errors.  Is the
order of these output lines unstable?  How do we "sort" these
bisect-all results?  If we are not sorting and the output depends on
happenstance, then probably we would need to compare the expected
and actual output after sorting.  Or if the output depends on
something under our control (e.g. they are related to topology and
relative commit timestamp), we probably should try to control that
"something" tighter so that we can rely on the order of the lines in
the "expect" file.

It also appears that we have "--bisect and --first-parent do not
work well together" in t6000, which also needs to be updated.  I
needed the following squashed into this patch to make "make test"
pass.

diff --git a/t/t6000-rev-list-misc.sh b/t/t6000-rev-list-misc.sh
index 969e4e9e52..981198ae6e 100755
--- a/t/t6000-rev-list-misc.sh
+++ b/t/t6000-rev-list-misc.sh
@@ -96,8 +96,8 @@ test_expect_success 'rev-list can show index objects' '
 	test_cmp expect actual
 '
 
-test_expect_success '--bisect and --first-parent can not be combined' '
-	test_must_fail git rev-list --bisect --first-parent HEAD
+test_expect_success '--bisect and --first-parent can now be combined' '
+	git rev-list --bisect --first-parent HEAD
 '
 
 test_expect_success '--header shows a NUL after each commit' '

Re: [RFC PATCH v4] Implement --first-parent for git rev-list --bisect

[Tiago Botelho]

On 28 May 2018 at 15:25, Junio C Hamano <gitster@pobox.com> wrote:

> Tiago Botelho <tiagonbotelho@gmail.com> writes:

> > 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.
> >
> > Signed-off-by: Tiago Botelho <tiagonbotelho@hotmail.com>
> > ---
> >
> > This patch adds all Junio's suggestions, namely do_find_bisection()
being
> > broken when assigning q's weight to p if in first parent mode and q
being
> > not UNINTERESTING and its weight still not being known.
> >
> > The graph displayed in the unit tests was also changed from being
top-bottom
> > to be left-right in order to keep it consistent with graphs in other
tests.
> >
> >  bisect.c                   | 45
++++++++++++++++++++++++++++++---------------
> >  bisect.h                   |  3 ++-
> >  builtin/rev-list.c         |  3 +++
> >  revision.c                 |  3 ---
> >  t/t6002-rev-list-bisect.sh | 37 +++++++++++++++++++++++++++++++++++++
> >  5 files changed, 72 insertions(+), 19 deletions(-)

> > diff --git a/t/t6002-rev-list-bisect.sh b/t/t6002-rev-list-bisect.sh
> > index a66140803..774d9a4fd 100755
> > --- a/t/t6002-rev-list-bisect.sh
> > +++ b/t/t6002-rev-list-bisect.sh
> > @@ -263,4 +263,41 @@ test_expect_success 'rev-parse --bisect can
default to good/bad refs' '
> > ...
> > +test_output_expect_success "--bisect-all --first-parent" 'git rev-list
--bisect-all --first-parent FX ^A' <<EOF
> > +$(git rev-parse EX) (dist=1)
> > +$(git rev-parse D) (dist=1)
> > +$(git rev-parse FX) (dist=0)
> > +EOF
> > +
> >  test_done

> Running this test number of times gives me spurious errors.  Is the
> order of these output lines unstable?  How do we "sort" these
> bisect-all results?  If we are not sorting and the output depends on
> happenstance, then probably we would need to compare the expected
> and actual output after sorting.  Or if the output depends on
> something under our control (e.g. they are related to topology and
> relative commit timestamp), we probably should try to control that
> "something" tighter so that we can rely on the order of the lines in
> the "expect" file.

The reason why the tests were failing was because the above "old" tests
did not make use of test_commit which in turn would make the sha of each
commit be different and as a result give unexpected outputs at times.
If I move them to the top of that file the tests will pass every time,
would that
be ok?

> It also appears that we have "--bisect and --first-parent do not
> work well together" in t6000, which also needs to be updated.  I
> needed the following squashed into this patch to make "make test"
> pass.

> diff --git a/t/t6000-rev-list-misc.sh b/t/t6000-rev-list-misc.sh
> index 969e4e9e52..981198ae6e 100755
> --- a/t/t6000-rev-list-misc.sh
> +++ b/t/t6000-rev-list-misc.sh
> @@ -96,8 +96,8 @@ test_expect_success 'rev-list can show index objects' '
>          test_cmp expect actual
>   '

> -test_expect_success '--bisect and --first-parent can not be combined' '
> -       test_must_fail git rev-list --bisect --first-parent HEAD
> +test_expect_success '--bisect and --first-parent can now be combined' '
> +       git rev-list --bisect --first-parent HEAD
>   '

>   test_expect_success '--header shows a NUL after each commit' '

Re: [RFC PATCH v4] Implement --first-parent for git rev-list --bisect

[Junio C Hamano]

Tiago Botelho <tiagonbotelho@gmail.com> writes:

>> Running this test number of times gives me spurious errors.  Is the
>> order of these output lines unstable?  How do we "sort" these
>> bisect-all results?  If we are not sorting and the output depends on
>> happenstance, then probably we would need to compare the expected
>> and actual output after sorting.  Or if the output depends on
>> something under our control (e.g. they are related to topology and
>> relative commit timestamp), we probably should try to control that
>> "something" tighter so that we can rely on the order of the lines in
>> the "expect" file.
>
> The reason why the tests were failing was because the above "old" tests
> did not make use of test_commit which in turn would make the sha of each
> commit be different and as a result give unexpected outputs at times.
> If I move them to the top of that file the tests will pass every time,
> would that
> be ok?

That means if somebody else needs to add other tests before the
location you are planning to move your tests, your tests would
suddenly start failing, no?  That does not sound like a particularly
robust solution to me.