sequencer (rebase -i): respect strategy/strategy_opts settings

The sequencer already has an idea about using different merge
strategies. We just piggy-back on top of that, using rebase -i's
own settings, when running the sequencer in interactive rebase mode.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sequencer.c

@@ -114,6 +114,8 @@ static GIT_PATH_FUNC(rebase_path_verbose, "rebase-merge/verbose")
 static GIT_PATH_FUNC(rebase_path_head_name, "rebase-merge/head-name")
 static GIT_PATH_FUNC(rebase_path_onto, "rebase-merge/onto")
 static GIT_PATH_FUNC(rebase_path_autostash, "rebase-merge/autostash")
+static GIT_PATH_FUNC(rebase_path_strategy, "rebase-merge/strategy")
+static GIT_PATH_FUNC(rebase_path_strategy_opts, "rebase-merge/strategy_opts")
 
 static inline int is_rebase_i(const struct replay_opts *opts)
 {
@@ -1368,6 +1370,26 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
 	return 0;
 }
 
+static void read_strategy_opts(struct replay_opts *opts, struct strbuf *buf)
+{
+	int i;
+
+	strbuf_reset(buf);
+	if (!read_oneliner(buf, rebase_path_strategy(), 0))
+		return;
+	opts->strategy = strbuf_detach(buf, NULL);
+	if (!read_oneliner(buf, rebase_path_strategy_opts(), 0))
+		return;
+
+	opts->xopts_nr = split_cmdline(buf->buf, (const char ***)&opts->xopts);
+	for (i = 0; i < opts->xopts_nr; i++) {
+		const char *arg = opts->xopts[i];
+
+		skip_prefix(arg, "--", &arg);
+		opts->xopts[i] = xstrdup(arg);
+	}
+}
+
 static int read_populate_opts(struct replay_opts *opts)
 {
 	if (is_rebase_i(opts)) {
@@ -1381,11 +1403,13 @@ static int read_populate_opts(struct replay_opts *opts)
 				opts->gpg_sign = xstrdup(buf.buf + 2);
 			}
 		}
-		strbuf_release(&buf);
 
 		if (file_exists(rebase_path_verbose()))
 			opts->verbose = 1;
 
+		read_strategy_opts(opts, &buf);
+		strbuf_release(&buf);
+
 		return 0;
 	}