simplify-merges: drop merge from irrelevant side branch

The merge simplification rule stated in 6546b59 (revision traversal:
show full history with merge simplification, 2008-07-31) still
treated merge commits too specially.  Namely, in a history with this
shape:

---o---o---M
/
x---x---x

where three 'x' were on a history completely unrelated to the main
history 'o' and do not touch any of the paths we are following, we
still said that after simplifying all of the parents of M, 'x'
(which is the leftmost 'x' that rightmost 'x simplifies down to) and
'o' (which would be the last commit on the main history that touches
the paths we are following) are independent from each other, and
both need to be kept.

That is incorrect; when the side branch 'x' never touches the paths,
it should be removed to allow M to simplify down to the last commit
on the main history that touches the paths.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/revision.c b/revision.c
index 33cb207f281f97f0eb1c24dd0b5200feda49848d..3536635a887c3c6c43cdc5c6d280a98d174b4a81 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -1424,6 +1424,22 @@ static struct merge_simplify_state *locate_simplify_state(struct rev_info *revs,
        return st;
 }
 
+static void remove_treesame_parents(struct commit *commit)
+{
+       struct commit_list **pp, *p;
+
+       pp = &commit->parents;
+       while ((p = *pp) != NULL) {
+               struct commit *parent = p->item;
+               if (parent->object.flags & TREESAME) {
+                       *pp = p->next;
+                       free(p);
+                       continue;
+               }
+               pp = &p->next;
+       }
+}
+
 static struct commit_list **simplify_one(struct rev_info *revs, struct commit *commit, struct commit_list **tail)
 {
        struct commit_list *p;
@@ -1469,6 +1485,13 @@ static struct commit_list **simplify_one(struct rev_info *revs, struct commit *c
                pst = locate_simplify_state(revs, p->item);
                p->item = pst->simplified;
        }
+
+       /*
+        * A merge with a tree-same parent is useless
+        */
+       if (commit->parents && commit->parents->next)
+               remove_treesame_parents(commit);
+
        cnt = remove_duplicate_parents(commit);
 
        /*

diff --git a/t/t6012-rev-list-simplify.sh b/t/t6012-rev-list-simplify.sh
index 510bb9679f29c10645c902caea020651a797aa2f..d6d79c467f70b08541be0254b37d0d63ea7da95d 100755 (executable)
--- a/t/t6012-rev-list-simplify.sh
+++ b/t/t6012-rev-list-simplify.sh
@@ -59,7 +59,23 @@ test_expect_success setup '
 
        echo "Final change" >file &&
        test_tick && git commit -a -m "Final change" &&
-       note I
+       note I &&
+
+       git symbolic-ref HEAD refs/heads/unrelated &&
+       git rm -f "*" &&
+       echo "Unrelated branch" >side &&
+       git add side &&
+       test_tick && git commit -m "Side root" &&
+       note J &&
+
+       git checkout master &&
+       test_tick && git merge -m "Coolest" unrelated &&
+       note K &&
+
+       echo "Immaterial" >elif &&
+       git add elif &&
+       test_tick && git commit -m "Last" &&
+       note L
 '
 
 FMT='tformat:%P        %H | %s'
@@ -82,10 +98,10 @@ check_result () {
        '
 }
 
-check_result 'I H G F E D C B A' --full-history
-check_result 'I H E C B A' --full-history -- file
-check_result 'I H E C B A' --full-history --topo-order -- file
-check_result 'I H E C B A' --full-history --date-order -- file
+check_result 'L K J I H G F E D C B A' --full-history
+check_result 'K I H E C B A' --full-history -- file
+check_result 'K I H E C B A' --full-history --topo-order -- file
+check_result 'K I H E C B A' --full-history --date-order -- file
 check_result 'I E C B A' --simplify-merges -- file
 check_result 'I B A' -- file
 check_result 'I B A' --topo-order -- file