builtin/merge.c: reduce parents early

Instead of waiting until we record the parents of resulting merge, reduce
redundant parents (including our HEAD) immediately after reading them.

The change to t7602 illustrates the essence of the effect of this change.
The octopus merge strategy used to be fed with redundant commits only to
discard them as "up-to-date", but we no longer feed such redundant commits
to it and the affected test degenerates to a regular two-head merge.

And obviously the known-to-be-broken test in t6028 is now fixed.

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

diff --git a/builtin/merge.c b/builtin/merge.c
index 2cef2f6a261377770329fa0fbfc51e5c3dc765c9..20aeca0b3c29f3c1c0e037b25f630eb0d9bbf34e 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -938,31 +938,22 @@ static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 }
 
 static int finish_automerge(struct commit *head,
+                           int head_subsumed,
                            struct commit_list *common,
                            struct commit_list *remoteheads,
                            unsigned char *result_tree,
                            const char *wt_strategy)
 {
-       struct commit_list *parents = NULL, *j;
+       struct commit_list *parents = NULL;
        struct strbuf buf = STRBUF_INIT;
        unsigned char result_commit[20];
 
        free_commit_list(common);
-       if (allow_fast_forward) {
-               parents = remoteheads;
+       parents = remoteheads;
+       if (!head_subsumed || !allow_fast_forward)
                commit_list_insert(head, &parents);
-               parents = reduce_heads(parents);
-       } else {
-               struct commit_list **pptr = &parents;
-
-               pptr = &commit_list_insert(head,
-                               pptr)->next;
-               for (j = remoteheads; j; j = j->next)
-                       pptr = &commit_list_insert(j->item, pptr)->next;
-       }
        strbuf_addch(&merge_msg, '\n');
        prepare_to_commit(remoteheads);
-       free_commit_list(remoteheads);
        if (commit_tree(&merge_msg, result_tree, parents, result_commit,
                        NULL, sign_commit))
                die(_("failed to write commit object"));
@@ -1137,12 +1128,16 @@ static int default_edit_option(void)
                st_stdin.st_mode == st_stdout.st_mode);
 }
 
-static struct commit_list *collect_parents(int argc, const char **argv)
+static struct commit_list *collect_parents(struct commit *head_commit,
+                                          int *head_subsumed,
+                                          int argc, const char **argv)
 {
        int i;
-       struct commit_list *remoteheads = NULL;
+       struct commit_list *remoteheads = NULL, *parents, *next;
        struct commit_list **remotes = &remoteheads;
 
+       if (head_commit)
+               remotes = &commit_list_insert(head_commit, remotes)->next;
        for (i = 0; i < argc; i++) {
                struct commit *commit = get_merge_parent(argv[i]);
                if (!commit)
@@ -1150,6 +1145,20 @@ static struct commit_list *collect_parents(int argc, const char **argv)
                remotes = &commit_list_insert(commit, remotes)->next;
        }
        *remotes = NULL;
+
+       parents = reduce_heads(remoteheads);
+
+       *head_subsumed = 1; /* we will flip this to 0 when we find it */
+       for (remoteheads = NULL, remotes = &remoteheads;
+            parents;
+            parents = next) {
+               struct commit *commit = parents->item;
+               next = parents->next;
+               if (commit == head_commit)
+                       *head_subsumed = 0;
+               else
+                       remotes = &commit_list_insert(commit, remotes)->next;
+       }
        return remoteheads;
 }
 
@@ -1161,7 +1170,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
        struct commit *head_commit;
        struct strbuf buf = STRBUF_INIT;
        const char *head_arg;
-       int flag, i, ret = 0;
+       int flag, i, ret = 0, head_subsumed;
        int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
        struct commit_list *common = NULL;
        const char *best_strategy = NULL, *wt_strategy = NULL;
@@ -1270,7 +1279,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                head_arg = argv[1];
                argv += 2;
                argc -= 2;
-               remoteheads = collect_parents(argc, argv);
+               remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
        } else if (!head_commit) {
                struct commit *remote_head;
                /*
@@ -1286,7 +1295,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                if (!allow_fast_forward)
                        die(_("Non-fast-forward commit does not make sense into "
                            "an empty head"));
-               remoteheads = collect_parents(argc, argv);
+               remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
                remote_head = remoteheads->item;
                if (!remote_head)
                        die(_("%s - not something we can merge"), argv[0]);
@@ -1305,7 +1314,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                 * the standard merge summary message to be appended
                 * to the given message.
                 */
-               remoteheads = collect_parents(argc, argv);
+               remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
                for (p = remoteheads; p; p = p->next)
                        merge_name(merge_remote_util(p->item)->name, &merge_names);
 
@@ -1351,7 +1360,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                option_edit = 0;
 
        if (!use_strategies) {
-               if (!remoteheads->next)
+               if (!remoteheads)
+                       ; /* already up-to-date */
+               else if (!remoteheads->next)
                        add_strategies(pull_twohead, DEFAULT_TWOHEAD);
                else
                        add_strategies(pull_octopus, DEFAULT_OCTOPUS);
@@ -1364,7 +1375,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                        allow_trivial = 0;
        }
 
-       if (!remoteheads->next)
+       if (!remoteheads)
+               ; /* already up-to-date */
+       else if (!remoteheads->next)
                common = get_merge_bases(head_commit, remoteheads->item, 1);
        else {
                struct commit_list *list = remoteheads;
@@ -1376,10 +1389,11 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
        update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
                   NULL, 0, DIE_ON_ERR);
 
-       if (!common)
+       if (remoteheads && !common)
                ; /* No common ancestors found. We need a real merge. */
-       else if (!remoteheads->next && !common->next &&
-                       common->item == remoteheads->item) {
+       else if (!remoteheads ||
+                (!remoteheads->next && !common->next &&
+                 common->item == remoteheads->item)) {
                /*
                 * If head can reach all the merge then we are up to date.
                 * but first the most common case of merging one remote.
@@ -1553,7 +1567,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
         * auto resolved the merge cleanly.
         */
        if (automerge_was_ok) {
-               ret = finish_automerge(head_commit, common, remoteheads,
+               ret = finish_automerge(head_commit, head_subsumed,
+                                      common, remoteheads,
                                       result_tree, wt_strategy);
                goto done;
        }

diff --git a/t/t6028-merge-up-to-date.sh b/t/t6028-merge-up-to-date.sh
index 824fca5b5b7efe1d472937732b2f55fb7aede830..c518e9c30ccbb12c504d25aa965f8941a3989d8d 100755 (executable)
--- a/t/t6028-merge-up-to-date.sh
+++ b/t/t6028-merge-up-to-date.sh
@@ -79,7 +79,7 @@ test_expect_success 'merge -s subtree up-to-date' '
 
 '
 
-test_expect_failure 'merge fast-forward octopus' '
+test_expect_success 'merge fast-forward octopus' '
 
        git reset --hard c0 &&
        test_tick &&

diff --git a/t/t7602-merge-octopus-many.sh b/t/t7602-merge-octopus-many.sh
index 83e917b9180814754f967164d8742b244a1257ae..7117b57ccc9e20a2a6f4d10705b8a5665db8b30e 100755 (executable)
--- a/t/t7602-merge-octopus-many.sh
+++ b/t/t7602-merge-octopus-many.sh
@@ -76,7 +76,7 @@ Merge made by the 'recursive' strategy.
  create mode 100644 c5.c
 EOF
 
-test_expect_failure 'merge reduces irrelevant remote heads' '
+test_expect_success 'merge reduces irrelevant remote heads' '
        GIT_MERGE_VERBOSITY=0 git merge c4 c5 >actual &&
        test_cmp expected actual
 '

diff --git a/t/t7603-merge-reduce-heads.sh b/t/t7603-merge-reduce-heads.sh
index f2934e8c25e71f50503aeccdb6cfd5696c3882f3..a3b08a6420f7576e2208a9350a6f129972e57c23 100755 (executable)
--- a/t/t7603-merge-reduce-heads.sh
+++ b/t/t7603-merge-reduce-heads.sh
@@ -119,7 +119,7 @@ test_expect_success 'fast-forward to redundant refs' '
        git merge c4 c5
 '
 
-test_expect_failure 'verify merge result' '
+test_expect_success 'verify merge result' '
        test $(git rev-parse HEAD) = $(git rev-parse c5)
 '