[PATCH v2] sequencer: handle rebase-merges for "onto" message

[Doan Tran Cong Danh <congdanhqx@gmail.com>]

In order to work correctly, git-rebase --rebase-merges needs to make
initial todo list with unique labels.

Those unique labels is being handled by employing a hashmap and
appending an unique number if any duplicate is found.

But, we forget that beside those labels for side branches,
we also have a special label `onto' for our so-called new-base.

In a special case that any of those labels for side branches named
`onto', git will run into trouble.

Correct it.

Signed-off-by: Doan Tran Cong Danh <congdanhqx@gmail.com>
---
Sorry for the noise, I forgot to check spelling for v1

And I forgot to delete From line when append to my MUA.

Range-diff against v1:
1:  48205889b4 ! 1:  9246beacf2 sequencer: handle rebase-merge for "onto" message
    @@ Metadata
     Author: Doan Tran Cong Danh <congdanhqx@gmail.com>
     
      ## Commit message ##
    -    sequencer: handle rebase-merge for "onto" message
    +    sequencer: handle rebase-merges for "onto" message
     
         In order to work correctly, git-rebase --rebase-merges needs to make
         initial todo list with unique labels.
     
         Those unique labels is being handled by employing a hashmap and
    -    suffixing an unique number if any duplicate is found.
    +    appending an unique number if any duplicate is found.
     
    -    But we forgat that beside of those labels for side branches,
    -    we also make a special label `onto' for our so-called new-base.
    +    But, we forget that beside those labels for side branches,
    +    we also have a special label `onto' for our so-called new-base.
     
         In a special case that any of those labels for side branches named
         `onto', git will run into trouble.

 sequencer.c              |  5 +++++
 t/t3430-rebase-merges.sh | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/sequencer.c b/sequencer.c
index 350045b1b4..fc81e43f0f 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -4569,10 +4569,15 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 	strbuf_init(&state.buf, 32);
 
 	if (revs->cmdline.nr && (revs->cmdline.rev[0].flags & BOTTOM)) {
+		struct labels_entry *onto_label_entry;
 		struct object_id *oid = &revs->cmdline.rev[0].item->oid;
 		FLEX_ALLOC_STR(entry, string, "onto");
 		oidcpy(&entry->entry.oid, oid);
 		oidmap_put(&state.commit2label, entry);
+
+		FLEX_ALLOC_STR(onto_label_entry, label, "onto");
+		hashmap_entry_init(&onto_label_entry->entry, strihash("onto"));
+		hashmap_add(&state.labels, &onto_label_entry->entry);
 	}
 
 	/*
diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index f728aba995..4e2c0ede51 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh
@@ -474,4 +474,25 @@ test_expect_success '--rebase-merges with commit that can generate bad character
 	git rebase --rebase-merges --force-rebase E
 '
 
+test_expect_success '--rebase-merges with message matched with onto label' '
+	git checkout -b onto-label E &&
+	git merge -m onto G &&
+	git rebase --rebase-merges --force-rebase E &&
+	test_cmp_graph <<-\EOF
+	*   onto
+	|\
+	| * G
+	| * F
+	* |   E
+	|\ \
+	| * | B
+	* | | D
+	| |/
+	|/|
+	* | C
+	|/
+	* A
+	EOF
+'
+
 test_done
-- 
2.24.0.10.gc61c3b979f.dirty