1 files changed, 40 insertions, 5 deletions

diff --git a/revision.c b/revision.c
index 2f646deab0..9dc55d4003 100644
--- a/revision.c
+++ b/revision.c
@@ -11,6 +11,7 @@
 #include "reflog-walk.h"
 #include "patch-ids.h"
 #include "decorate.h"
+#include "log-tree.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -199,6 +200,8 @@ static struct commit *handle_commit(struct rev_info *revs, struct object *object
 			mark_parents_uninteresting(commit);
 			revs->limited = 1;
 		}
+		if (revs->show_source && !commit->util)
+			commit->util = (void *) name;
 		return commit;
 	}
 
@@ -292,10 +295,31 @@ static void file_change(struct diff_options *options,
 	DIFF_OPT_SET(options, HAS_CHANGES);
 }
 
-static int rev_compare_tree(struct rev_info *revs, struct tree *t1, struct tree *t2)
+static int rev_compare_tree(struct rev_info *revs, struct commit *parent, struct commit *commit)
 {
+	struct tree *t1 = parent->tree;
+	struct tree *t2 = commit->tree;
+
 	if (!t1)
 		return REV_TREE_NEW;
+
+	if (revs->simplify_by_decoration) {
+		/*
+		 * If we are simplifying by decoration, then the commit
+		 * is worth showing if it has a tag pointing at it.
+		 */
+		if (lookup_decoration(&name_decoration, &commit->object))
+			return REV_TREE_DIFFERENT;
+		/*
+		 * A commit that is not pointed by a tag is uninteresting
+		 * if we are not limited by path.  This means that you will
+		 * see the usual "commits that touch the paths" plus any
+		 * tagged commit by specifying both --simplify-by-decoration
+		 * and pathspec.
+		 */
+		if (!revs->prune_data)
+			return REV_TREE_SAME;
+	}
 	if (!t2)
 		return REV_TREE_DIFFERENT;
 	tree_difference = REV_TREE_SAME;
@@ -306,12 +330,13 @@ static int rev_compare_tree(struct rev_info *revs, struct tree *t1, struct tree
 	return tree_difference;
 }
 
-static int rev_same_tree_as_empty(struct rev_info *revs, struct tree *t1)
+static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 {
 	int retval;
 	void *tree;
 	unsigned long size;
 	struct tree_desc empty, real;
+	struct tree *t1 = commit->tree;
 
 	if (!t1)
 		return 0;
@@ -345,7 +370,7 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 		return;
 
 	if (!commit->parents) {
-		if (rev_same_tree_as_empty(revs, commit->tree))
+		if (rev_same_tree_as_empty(revs, commit))
 			commit->object.flags |= TREESAME;
 		return;
 	}
@@ -365,7 +390,7 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 			die("cannot simplify commit %s (because of %s)",
 			    sha1_to_hex(commit->object.sha1),
 			    sha1_to_hex(p->object.sha1));
-		switch (rev_compare_tree(revs, p->tree, commit->tree)) {
+		switch (rev_compare_tree(revs, p, commit)) {
 		case REV_TREE_SAME:
 			tree_same = 1;
 			if (!revs->simplify_history || (p->object.flags & UNINTERESTING)) {
@@ -385,7 +410,7 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 
 		case REV_TREE_NEW:
 			if (revs->remove_empty_trees &&
-			    rev_same_tree_as_empty(revs, p->tree)) {
+			    rev_same_tree_as_empty(revs, p)) {
 				/* We are adding all the specified
 				 * paths from this parent, so the
 				 * history beyond this parent is not
@@ -484,6 +509,8 @@ static int add_parents_to_list(struct rev_info *revs, struct commit *commit,
 
 		if (parse_commit(p) < 0)
 			return -1;
+		if (revs->show_source && !p->util)
+			p->util = commit->util;
 		p->object.flags |= left_flag;
 		if (!(p->object.flags & SEEN)) {
 			p->object.flags |= SEEN;
@@ -1033,6 +1060,14 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->rewrite_parents = 1;
 		revs->simplify_history = 0;
 		revs->limited = 1;
+	} else if (!strcmp(arg, "--simplify-by-decoration")) {
+		revs->simplify_merges = 1;
+		revs->rewrite_parents = 1;
+		revs->simplify_history = 0;
+		revs->simplify_by_decoration = 1;
+		revs->limited = 1;
+		revs->prune = 1;
+		load_ref_decorations();
 	} else if (!strcmp(arg, "--date-order")) {
 		revs->lifo = 0;
 		revs->topo_order = 1;