Re: [PATCH v2 2/2] rebase --exec: make it work with --rebase-merges

From: Johannes Schindelin <redacted>

The idea of `--exec` is to append an `exec` call after each `pick`.

Since the introduction of fixup!/squash! commits, this idea was extended
to apply to "pick, possibly followed by a fixup/squash chain", i.e. an
exec would not be inserted between a `pick` and any of its corresponding
`fixup` or `squash` lines.

The current implementation uses a dirty trick to achieve that: it
assumes that there are only pick/fixup/squash commands, and then
*inserts* the `exec` lines before any `pick` but the first, and appends
a final one.

With the todo lists generated by `git rebase --rebase-merges`, this
simple implementation shows its problems: it produces the exact wrong
thing when there are `label`, `reset` and `merge` commands.

Let's change the implementation to do exactly what we want: look for
`pick` lines, skip any fixup/squash chains, and then insert the `exec`
line. Lather, rinse, repeat.

While at it, also add `exec` lines after `merge` commands, because they
are similar in spirit to `pick` commands: they add new commits.

Signed-off-by: Johannes Schindelin <redacted>
---
  sequencer.c              | 37 +++++++++++++++++++++++++++----------
  t/t3430-rebase-merges.sh |  2 +-
  2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 31038472f..ed2e694ff 100644
--- a/sequencer.c
+++ b/sequencer.c

@@ -4244,10 +4244,9 @@ int sequencer_add_exec_commands(const char *commands)
  {
  	const char *todo_file = rebase_path_todo();
  	struct todo_list todo_list = TODO_LIST_INIT;
-	struct todo_item *item;
  	struct strbuf *buf = &todo_list.buf;
  	size_t offset = 0, commands_len = strlen(commands);
-	int i, first;
+	int i, insert;
  
  	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
  		return error(_("could not read '%s'."), todo_file);

@@ -4257,19 +4256,37 @@ int sequencer_add_exec_commands(const char *commands)
  		return error(_("unusable todo list: '%s'"), todo_file);
  	}
  
-	first = 1;
-	/* insert <commands> before every pick except the first one */
-	for (item = todo_list.items, i = 0; i < todo_list.nr; i++, item++) {
-		if (item->command == TODO_PICK && !first) {
-			strbuf_insert(buf, item->offset_in_buf + offset,
-				      commands, commands_len);
+	/*
+	 * Insert <commands> after every pick. Here, fixup/squash chains
+	 * are considered part of the pick, so we insert the commands *after*
+	 * those chains if there are any.
+	 */
+	insert = -1;
+	for (i = 0; i < todo_list.nr; i++) {
+		enum todo_command command = todo_list.items[i].command;
+
+		if (insert >= 0) {
+			/* skip fixup/squash chains */
+			if (command == TODO_COMMENT)
+				continue;

  
  	i = write_message(buf->buf, buf->len, todo_file, 0);
  	todo_list_release(&todo_list);

diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index 0bf5eaa37..90ae613e2 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh

@@ -363,7 +363,7 @@ test_expect_success 'octopus merges' '
  	EOF
  '
  
-test_expect_failure 'with --autosquash and --exec' '
+test_expect_success 'with --autosquash and --exec' '
  	git checkout -b with-exec H &&
  	echo Booh >B.t &&
  	test_tick &&