From f1e2426b28399b563527d110c849acd65b680de6 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Mon, 1 Aug 2016 13:44:50 +0200
Subject: [PATCH] merge-recursive: offer an option to retain the output in
 'obuf'

Since 66a155b (Enable output buffering in merge-recursive., 2007-01-14),
we already accumulate the output in a buffer. The idea was to avoid
interfering with the progress output that goes to stderr, which is
unbuffered, when we write to stdout, which is buffered.

We extend that buffering to allow the caller to handle the output
(possibly suppressing it). This will help us when extending the
sequencer to do rebase -i's brunt work: it does not want the picks to
print anything by default but instead determine itself whether to print
the output or not.

Note that we also redirect the error messages into the output buffer
when the caller asked not to flush the output buffer, for two reasons:
1) to retain the correct output order, and 2) to allow the caller to
suppress *all* output.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 merge-recursive.c | 17 +++++++++++++----
 merge-recursive.h |  2 +-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index 99c963558b..ec50932210 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -25,7 +25,7 @@
 
 static void flush_output(struct merge_options *o)
 {
-	if (o->obuf.len) {
+	if (o->buffer_output < 2 && o->obuf.len) {
 		fputs(o->obuf.buf, stdout);
 		strbuf_reset(&o->obuf);
 	}
@@ -35,12 +35,21 @@ static int err(struct merge_options *o, const char *err, ...)
 {
 	va_list params;
 
-	flush_output(o);
+	if (o->buffer_output < 2)
+		flush_output(o);
+	else {
+		strbuf_complete(&o->obuf, '\n');
+		strbuf_addstr(&o->obuf, "error: ");
+	}
 	va_start(params, err);
 	strbuf_vaddf(&o->obuf, err, params);
 	va_end(params);
-	error("%s", o->obuf.buf);
-	strbuf_reset(&o->obuf);
+	if (o->buffer_output > 1)
+		strbuf_addch(&o->obuf, '\n');
+	else {
+		error("%s", o->obuf.buf);
+		strbuf_reset(&o->obuf);
+	}
 
 	return -1;
 }
diff --git a/merge-recursive.h b/merge-recursive.h
index d415724aea..735343b413 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -13,7 +13,7 @@ struct merge_options {
 		MERGE_RECURSIVE_THEIRS
 	} recursive_variant;
 	const char *subtree_shift;
-	unsigned buffer_output : 1;
+	unsigned buffer_output; /* 1: output at end, 2: keep buffered */
 	unsigned renormalize : 1;
 	long xdl_opts;
 	int verbosity;