rebase: simplify code related to imply_merge()

The code's evolution left in some bits surrounding enum rebase_type that
don't really make sense any more. In particular, it makes no sense to
invoke imply_merge() if the type is already known not to be
REBASE_APPLY, and it makes no sense to assign the type after calling
imply_merge().

enum rebase_type had more values until commit a74b350 ("rebase: drop
support for `--preserve-merges`") and commit 10cdb9f ("rebase: rename
the two primary rebase backends"). The latter commit also renamed
imply_interactive() to imply_merge().

Signed-off-by: Oswald Buddenhagen <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ossilator

builtin/rebase.c

@@ -386,7 +386,6 @@ static int parse_opt_keep_empty(const struct option *opt, const char *arg,
 
 	imply_merge(opts, unset ? "--no-keep-empty" : "--keep-empty");
 	opts->keep_empty = !unset;
-	opts->type = REBASE_MERGE;
 	return 0;
 }
 
@@ -1505,9 +1504,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-	if (options.type == REBASE_MERGE)
-		imply_merge(&options, "--merge");
-
 	if (options.root && !options.onto_name)
 		imply_merge(&options, "--root without --onto");
 
@@ -1552,7 +1548,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	if (options.type == REBASE_UNSPECIFIED) {
 		if (!strcmp(options.default_backend, "merge"))
-			imply_merge(&options, "--merge");
+			options.type = REBASE_MERGE;
 		else if (!strcmp(options.default_backend, "apply"))
 			options.type = REBASE_APPLY;
 		else