revision: introduce prepare_revision_walk_extended()rs/revision-keep-pending

prepare_revision_walk() allows callers to take ownership of the array of
pending objects by setting the rev_info flag "leak_pending" and copying
the object_array "pending".  They use it to clear commit marks after
setup is done.  This interface is brittle enough that it requires
extensive comments.

Provide an easier way by adding a function that can hand over the array
to a caller-supplied output parameter and converting all users of the
flag "leak_pending" to call prepare_revision_walk_extended() instead.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

6 files changed, 24 insertions, 41 deletions

diff --git a/Documentation/technical/api-revision-walking.txt b/Documentation/technical/api-revision-walking.txt
index 55b878ade8..9dc573d2ec 100644
--- a/Documentation/technical/api-revision-walking.txt
+++ b/Documentation/technical/api-revision-walking.txt
@@ -50,6 +50,12 @@ function.
 	returns any error (non-zero return code) and if it does not, you can
 	start using get_revision() to do the iteration.
 
+`prepare_revision_walk_extended`::
+
+	Like prepare_revision_walk(), but allows callers to take ownership
+	of the array of pending objects by passing an object_array pointer
+	as the second parameter; passing NULL clears the array.
+
 `get_revision`::
 
 	Takes a pointer to a `rev_info` structure and iterates over it,
diff --git a/bisect.c b/bisect.c
index 3756f127b0..3539cc9c61 100644
--- a/bisect.c
+++ b/bisect.c
@@ -636,9 +636,10 @@ static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
 	/* XXX leak rev_argv, as "revs" may still be pointing to it */
 }
 
-static void bisect_common(struct rev_info *revs)
+static void bisect_common(struct rev_info *revs,
+			  struct object_array *old_pending_ptr)
 {
-	if (prepare_revision_walk(revs))
+	if (prepare_revision_walk_extended(revs, old_pending_ptr))
 		die("revision walk setup failed");
 	if (revs->tree_objects)
 		mark_edges_uninteresting(revs, NULL);
@@ -819,15 +820,7 @@ static int check_ancestors(const char *prefix)
 	bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
 
 	/* Save pending objects, so they can be cleaned up later. */
-	pending_copy = revs.pending;
-	revs.leak_pending = 1;
-
-	/*
-	 * bisect_common calls prepare_revision_walk right away, which
-	 * (together with .leak_pending = 1) makes us the sole owner of
-	 * the list of pending objects.
-	 */
-	bisect_common(&revs);
+	bisect_common(&revs, &pending_copy);
 	res = (revs.commits != NULL);
 
 	/* Clean up objects used, as they will be reused. */
@@ -958,7 +951,7 @@ int bisect_next_all(const char *prefix, int no_checkout)
 	bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
 	revs.limited = 1;
 
-	bisect_common(&revs);
+	bisect_common(&revs, NULL);
 
 	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
 	revs.commits = managed_skipped(revs.commits, &tried);
diff --git a/builtin/checkout.c b/builtin/checkout.c
index fc4f8fd2ea..d94385155c 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -798,14 +798,7 @@ static void orphaned_commit_warning(struct commit *old, struct commit *new)
 	add_pending_oid(&revs, "HEAD", &new->object.oid, UNINTERESTING);
 
 	/* Save pending objects, so they can be cleaned up later. */
-	refs = revs.pending;
-	revs.leak_pending = 1;
-
-	/*
-	 * prepare_revision_walk (together with .leak_pending = 1) makes us
-	 * the sole owner of the list of pending objects.
-	 */
-	if (prepare_revision_walk(&revs))
+	if (prepare_revision_walk_extended(&revs, &refs))
 		die(_("internal error in revision walk"));
 	if (!(old->object.flags & UNINTERESTING))
 		suggest_reattach(old, &revs);
diff --git a/bundle.c b/bundle.c
index c092d5d68f..ed0f70c07d 100644
--- a/bundle.c
+++ b/bundle.c
@@ -158,14 +158,7 @@ int verify_bundle(struct bundle_header *header, int verbose)
 	setup_revisions(2, argv, &revs, NULL);
 
 	/* Save pending objects, so they can be cleaned up later. */
-	refs = revs.pending;
-	revs.leak_pending = 1;
-
-	/*
-	 * prepare_revision_walk (together with .leak_pending = 1) makes us
-	 * the sole owner of the list of pending objects.
-	 */
-	if (prepare_revision_walk(&revs))
+	if (prepare_revision_walk_extended(&revs, &refs))
 		die(_("revision walk setup failed"));
 
 	i = req_nr;
diff --git a/revision.c b/revision.c
index d167223e69..21c53148cd 100644
--- a/revision.c
+++ b/revision.c
@@ -2832,6 +2832,12 @@ void reset_revision_walk(void)
 
 int prepare_revision_walk(struct rev_info *revs)
 {
+	return prepare_revision_walk_extended(revs, NULL);
+}
+
+int prepare_revision_walk_extended(struct rev_info *revs,
+				   struct object_array *old_pending_ptr)
+{
 	int i;
 	struct object_array old_pending;
 	struct commit_list **next = &revs->commits;
@@ -2850,7 +2856,9 @@ int prepare_revision_walk(struct rev_info *revs)
 			}
 		}
 	}
-	if (!revs->leak_pending)
+	if (old_pending_ptr)
+		*old_pending_ptr = old_pending;
+	else
 		object_array_clear(&old_pending);
 
 	/* Signal whether we need per-parent treesame decoration */
diff --git a/revision.h b/revision.h
index 54761200ad..5d4b475334 100644
--- a/revision.h
+++ b/revision.h
@@ -150,18 +150,6 @@ struct rev_info {
 			date_mode_explicit:1,
 			preserve_subject:1;
 	unsigned int	disable_stdin:1;
-	/*
-	 * Set `leak_pending` to prevent `prepare_revision_walk()` from clearing
-	 * the array of pending objects (`pending`). It will still forget about
-	 * the array and its entries, so they really are leaked. This can be
-	 * useful if the `struct object_array` `pending` is copied before
-	 * calling `prepare_revision_walk()`. By setting `leak_pending`, you
-	 * effectively claim ownership of the old array, so you should most
-	 * likely call `object_array_clear(&pending_copy)` once you are done.
-	 * Observe that this is about ownership of the array and its entries,
-	 * not the commits referenced by those entries.
-	 */
-	unsigned int	leak_pending:1;
 	/* --show-linear-break */
 	unsigned int	track_linear:1,
 			track_first_time:1,
@@ -270,6 +258,8 @@ extern int handle_revision_arg(const char *arg, struct rev_info *revs,
 
 extern void reset_revision_walk(void);
 extern int prepare_revision_walk(struct rev_info *revs);
+extern int prepare_revision_walk_extended(struct rev_info *revs,
+					  struct object_array *old_pending_ptr);
 extern struct commit *get_revision(struct rev_info *revs);
 extern char *get_revision_mark(const struct rev_info *revs,
 			       const struct commit *commit);