merge: clarify call chain

prepare_to_commit() cannot be reached in the non-squash case:
It is called by merge_trivial() and finish_automerge() only, but the
calls to the latter are somewhat hard to track:

If option_commit is not set, the code in cmd_merge() uses a fake
conflict return code (ret=1) to avoid writing the tree, which also
avoids setting automerge_was_ok (just as in the proper ret==1 case), so
that finish_automerge() is not called.

To ensure that no code change breaks that assumption, safe-guard
prepare_to_commit() by a BUG() statement.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Michael J Gruber <git@grubix.eu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/merge.c b/builtin/merge.c
index 900bafdb45d0b28ab5497cfd251535266fc92be5..2d79e79c5b11a437ce91b34b56f31b1157af54db 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -761,6 +761,8 @@ static void prepare_to_commit(struct commit_list *remoteheads)
        struct strbuf msg = STRBUF_INIT;
        strbuf_addbuf(&msg, &merge_msg);
        strbuf_addch(&msg, '\n');
+       if (squash)
+               BUG("the control must not reach here under --squash");
        if (0 < option_edit)
                strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
        write_file_buf(git_path_merge_msg(), msg.buf, msg.len);