revision walker: mini clean-up

This removes the unnecessary indirection of "revs->prune_fn",
since that function is always the same one (or NULL), and there
is in fact not even an abstraction reason to make it a function
(i.e. its not called from some other file and doesn't allow us
to keep the function itself static or anything like that).

It then just replaces it with a bit that says "prune or not",
and if not pruning, every commit gets TREECHANGE.

That in turn means that

 - if (!revs->prune_fn || (flags & TREECHANGE))
 - if (revs->prune_fn && !(flags & TREECHANGE))

just become

 - if (flags & TREECHANGE)
 - if (!(flags & TREECHANGE))

respectively.

Together with adding the "single_parent()" helper function, the "complex"
conditional now becomes

	if (!(flags & TREECHANGE) && rev->dense && single_parent(commit))
		continue;

Also indirection of "revs->dense" checking is thrown away the
same way, because TREECHANGE bit is set appropriately now.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/revision.c b/revision.c
index 2e6121f..931f978 100644
--- a/revision.c
+++ b/revision.c
@@ -308,6 +308,14 @@
 	struct commit_list **pp, *parent;
 	int tree_changed = 0, tree_same = 0;
 
+	/*
+	 * If we don't do pruning, everything is interesting
+	 */
+	if (!revs->prune) {
+		commit->object.flags |= TREECHANGE;
+		return;
+	}
+
 	if (!commit->tree)
 		return;
 
@@ -317,6 +325,15 @@
 		return;
 	}
 
+	/*
+	 * Normal non-merge commit? If we don't want to make the
+	 * history dense, we consider it always to be a change..
+	 */
+	if (!revs->dense && !commit->parents->next) {
+		commit->object.flags |= TREECHANGE;
+		return;
+	}
+
 	pp = &commit->parents;
 	while ((parent = *pp) != NULL) {
 		struct commit *p = parent->item;
@@ -415,8 +432,7 @@
 	 * simplify the commit history and find the parent
 	 * that has no differences in the path set if one exists.
 	 */
-	if (revs->prune_fn)
-		revs->prune_fn(revs, commit);
+	try_to_simplify_commit(revs, commit);
 
 	if (revs->no_walk)
 		return 0;
@@ -684,9 +700,6 @@
 	revs->skip_count = -1;
 	revs->max_count = -1;
 
-	revs->prune_fn = NULL;
-	revs->prune_data = NULL;
-
 	revs->commit_format = CMIT_FMT_DEFAULT;
 
 	diff_setup(&revs->diffopt);
@@ -1271,7 +1284,7 @@
 		diff_tree_setup_paths(revs->prune_data, &revs->pruning);
 		/* Can't prune commits with rename following: the paths change.. */
 		if (!revs->diffopt.follow_renames)
-			revs->prune_fn = try_to_simplify_commit;
+			revs->prune = 1;
 		if (!revs->full_diff)
 			diff_tree_setup_paths(revs->prune_data, &revs->diffopt);
 	}
@@ -1412,7 +1425,7 @@
 		return commit_ignore;
 	if (!commit_match(commit, revs))
 		return commit_ignore;
-	if (revs->prune_fn && revs->dense) {
+	if (revs->prune && revs->dense) {
 		/* Commit without changes? */
 		if (!(commit->object.flags & TREECHANGE)) {
 			/* drop merges unless we want parenthood */