commit-reach: move can_all_from_reach_with_flags

There are several commit walks in the codebase. Group them together into
a new commit-reach.c file and corresponding header. After we group these
walks into one place, we can reduce duplicate logic by calling
equivalent methods.

The can_all_from_reach_with_flags method is used in a stateful way by
upload-pack.c. The parameters are very flexible, so we will be able to
use its commit walking logic for many other callers.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 80 insertions, 71 deletions

diff --git a/commit-reach.c b/commit-reach.c
index 01d796f011..d806291d5d 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -10,6 +10,7 @@
 #include "commit-reach.h"
 
 /* Remember to update object flag allocation in object.h */
+#define REACHABLE       (1u<<15)
 #define PARENT1		(1u<<16)
 #define PARENT2		(1u<<17)
 #define STALE		(1u<<18)
@@ -532,3 +533,65 @@ int commit_contains(struct ref_filter *filter, struct commit *commit,
 		return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
 	return is_descendant_of(commit, list);
 }
+
+int reachable(struct commit *from, unsigned int with_flag,
+	      unsigned int assign_flag, time_t min_commit_date)
+{
+	struct prio_queue work = { compare_commits_by_commit_date };
+
+	prio_queue_put(&work, from);
+	while (work.nr) {
+		struct commit_list *list;
+		struct commit *commit = prio_queue_get(&work);
+
+		if (commit->object.flags & with_flag) {
+			from->object.flags |= assign_flag;
+			break;
+		}
+		if (!commit->object.parsed)
+			parse_object(the_repository, &commit->object.oid);
+		if (commit->object.flags & REACHABLE)
+			continue;
+		commit->object.flags |= REACHABLE;
+		if (commit->date < min_commit_date)
+			continue;
+		for (list = commit->parents; list; list = list->next) {
+			struct commit *parent = list->item;
+			if (!(parent->object.flags & REACHABLE))
+				prio_queue_put(&work, parent);
+		}
+	}
+	from->object.flags |= REACHABLE;
+	clear_commit_marks(from, REACHABLE);
+	clear_prio_queue(&work);
+	return (from->object.flags & assign_flag);
+}
+
+int can_all_from_reach_with_flag(struct object_array *from,
+				 unsigned int with_flag,
+				 unsigned int assign_flag,
+				 time_t min_commit_date)
+{
+	int i;
+
+	for (i = 0; i < from->nr; i++) {
+		struct object *from_one = from->objects[i].item;
+
+		if (from_one->flags & assign_flag)
+			continue;
+		from_one = deref_tag(the_repository, from_one, "a from object", 0);
+		if (!from_one || from_one->type != OBJ_COMMIT) {
+			/* no way to tell if this is reachable by
+			 * looking at the ancestry chain alone, so
+			 * leave a note to ourselves not to worry about
+			 * this object anymore.
+			 */
+			from->objects[i].item->flags |= assign_flag;
+			continue;
+		}
+		if (!reachable((struct commit *)from_one, with_flag, assign_flag,
+			       min_commit_date))
+			return 0;
+	}
+	return 1;
+}
diff --git a/commit-reach.h b/commit-reach.h
index 13dec25cee..b28bc22fcd 100644
--- a/commit-reach.h
+++ b/commit-reach.h
@@ -59,4 +59,18 @@ define_commit_slab(contains_cache, enum contains_result);
 int commit_contains(struct ref_filter *filter, struct commit *commit,
 		    struct commit_list *list, struct contains_cache *cache);
 
+int reachable(struct commit *from, unsigned int with_flag,
+	      unsigned int assign_flag, time_t min_commit_date);
+
+/*
+ * Determine if every commit in 'from' can reach at least one commit
+ * that is marked with 'with_flag'. As we traverse, use 'assign_flag'
+ * as a marker for commits that are already visited. Do not walk
+ * commits with date below 'min_commit_date'.
+ */
+int can_all_from_reach_with_flag(struct object_array *from,
+				 unsigned int with_flag,
+				 unsigned int assign_flag,
+				 time_t min_commit_date);
+
 #endif
diff --git a/object.h b/object.h
index 18c2b073e3..b132944c51 100644
--- a/object.h
+++ b/object.h
@@ -60,12 +60,12 @@ struct object_array {
  * revision.h:               0---------10                                26
  * fetch-pack.c:             0----5
  * walker.c:                 0-2
- * upload-pack.c:                4       11----------------19
+ * upload-pack.c:                4       11-----14  16-----19
  * builtin/blame.c:                        12-13
  * bisect.c:                                        16
  * bundle.c:                                        16
  * http-push.c:                                     16-----19
- * commit-reach.c:                                  16-----19
+ * commit-reach.c:                                15-------19
  * sha1-name.c:                                              20
  * list-objects-filter.c:                                      21
  * builtin/fsck.c:           0--3
diff --git a/upload-pack.c b/upload-pack.c
index 427de461d8..11c426685d 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -24,13 +24,13 @@
 #include "quote.h"
 #include "upload-pack.h"
 #include "serve.h"
+#include "commit-reach.h"
 
 /* Remember to update object flag allocation in object.h */
 #define THEY_HAVE	(1u << 11)
 #define OUR_REF		(1u << 12)
 #define WANTED		(1u << 13)
 #define COMMON_KNOWN	(1u << 14)
-#define REACHABLE	(1u << 15)
 
 #define SHALLOW		(1u << 16)
 #define NOT_SHALLOW	(1u << 17)
@@ -336,74 +336,6 @@ static int got_oid(const char *hex, struct object_id *oid)
 	return 0;
 }
 
-static int reachable(struct commit *from, unsigned int with_flag,
-		     unsigned int assign_flag, time_t min_commit_date)
-{
-	struct prio_queue work = { compare_commits_by_commit_date };
-
-	prio_queue_put(&work, from);
-	while (work.nr) {
-		struct commit_list *list;
-		struct commit *commit = prio_queue_get(&work);
-
-		if (commit->object.flags & with_flag) {
-			from->object.flags |= assign_flag;
-			break;
-		}
-		if (!commit->object.parsed)
-			parse_object(the_repository, &commit->object.oid);
-		if (commit->object.flags & REACHABLE)
-			continue;
-		commit->object.flags |= REACHABLE;
-		if (commit->date < min_commit_date)
-			continue;
-		for (list = commit->parents; list; list = list->next) {
-			struct commit *parent = list->item;
-			if (!(parent->object.flags & REACHABLE))
-				prio_queue_put(&work, parent);
-		}
-	}
-	from->object.flags |= REACHABLE;
-	clear_commit_marks(from, REACHABLE);
-	clear_prio_queue(&work);
-	return (from->object.flags & assign_flag);
-}
-
-/*
- * Determine if every commit in 'from' can reach at least one commit
- * that is marked with 'with_flag'. As we traverse, use 'assign_flag'
- * as a marker for commits that are already visited. Do not walk
- * commits with date below 'min_commit_date'.
- */
-static int can_all_from_reach_with_flag(struct object_array *from,
-					unsigned int with_flag,
-					unsigned int assign_flag,
-					time_t min_commit_date)
-{
-	int i;
-
-	for (i = 0; i < from->nr; i++) {
-		struct object *from_one = from->objects[i].item;
-
-		if (from_one->flags & assign_flag)
-			continue;
-		from_one = deref_tag(the_repository, from_one, "a from object", 0);
-		if (!from_one || from_one->type != OBJ_COMMIT) {
-			/* no way to tell if this is reachable by
-			 * looking at the ancestry chain alone, so
-			 * leave a note to ourselves not to worry about
-			 * this object anymore.
-			 */
-			from->objects[i].item->flags |= assign_flag;
-			continue;
-		}
-		if (!reachable((struct commit *)from_one, with_flag, assign_flag,
-			       min_commit_date))
-			return 0;
-	}
-	return 1;
-}
-
 static int ok_to_give_up(void)
 {
 	if (!have_obj.nr)