rev-list: factor out bitmap-optimized routines

There are a few operations in rev-list that are optimized for bitmaps.
Rather than having the code inline in cmd_rev_list(), let's move them
into helpers. This not only makes the flow of the main function simpler,
but it lets us replace the complex "can we do the optimization?"
conditionals with a series of early returns from the functions. That
also makes it easy to add comments explaining those conditions.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 4cb5a52dee36bd0c03792dc62dad75e62cdd0e63..38c5ca5603bf2f70986fcd9903fb75d6ace4735d 100644 (file)
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -364,6 +364,69 @@ static inline int parse_missing_action_value(const char *value)
        return 0;
 }
 
+static int try_bitmap_count(struct rev_info *revs)
+{
+       uint32_t commit_count;
+       int max_count;
+       struct bitmap_index *bitmap_git;
+
+       /* This function only handles counting, not general traversal. */
+       if (!revs->count)
+               return -1;
+
+       /*
+        * A bitmap result can't know left/right, etc, because we don't
+        * actually traverse.
+        */
+       if (revs->left_right || revs->cherry_mark)
+               return -1;
+
+       /*
+        * This must be saved before doing any walking, since the revision
+        * machinery will count it down to zero while traversing.
+        */
+       max_count = revs->max_count;
+
+       bitmap_git = prepare_bitmap_walk(revs);
+       if (!bitmap_git)
+               return -1;
+
+       count_bitmap_commit_list(bitmap_git, &commit_count, NULL, NULL, NULL);
+       if (max_count >= 0 && max_count < commit_count)
+               commit_count = max_count;
+
+       printf("%d\n", commit_count);
+       free_bitmap_index(bitmap_git);
+       return 0;
+}
+
+static int try_bitmap_traversal(struct rev_info *revs)
+{
+       struct bitmap_index *bitmap_git;
+
+       /*
+        * We can't use a bitmap result with a traversal limit, since the set
+        * of commits we'd get would be essentially random.
+        */
+       if (revs->max_count >= 0)
+               return -1;
+
+       /*
+        * Our bitmap result will return all objects, and we're not
+        * yet prepared to show only particular types.
+        */
+       if (!revs->tag_objects || !revs->tree_objects || !revs->blob_objects)
+               return -1;
+
+       bitmap_git = prepare_bitmap_walk(revs);
+       if (!bitmap_git)
+               return -1;
+
+       traverse_bitmap_commit_list(bitmap_git, &show_object_fast);
+       free_bitmap_index(bitmap_git);
+       return 0;
+}
+
 int cmd_rev_list(int argc, const char **argv, const char *prefix)
 {
        struct rev_info revs;
@@ -534,27 +597,10 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
                progress = start_delayed_progress(show_progress, 0);
 
        if (use_bitmap_index) {
-               if (revs.count && !revs.left_right && !revs.cherry_mark) {
-                       uint32_t commit_count;
-                       int max_count = revs.max_count;
-                       struct bitmap_index *bitmap_git;
-                       if ((bitmap_git = prepare_bitmap_walk(&revs))) {
-                               count_bitmap_commit_list(bitmap_git, &commit_count, NULL, NULL, NULL);
-                               if (max_count >= 0 && max_count < commit_count)
-                                       commit_count = max_count;
-                               printf("%d\n", commit_count);
-                               free_bitmap_index(bitmap_git);
-                               return 0;
-                       }
-               } else if (revs.max_count < 0 &&
-                          revs.tag_objects && revs.tree_objects && revs.blob_objects) {
-                       struct bitmap_index *bitmap_git;
-                       if ((bitmap_git = prepare_bitmap_walk(&revs))) {
-                               traverse_bitmap_commit_list(bitmap_git, &show_object_fast);
-                               free_bitmap_index(bitmap_git);
-                               return 0;
-                       }
-               }
+               if (!try_bitmap_count(&revs))
+                       return 0;
+               if (!try_bitmap_traversal(&revs))
+                       return 0;
        }
 
        if (prepare_revision_walk(&revs))