Re: [GSoC][PATCH v2 5/7] sequencer: add a new function to silence a command, except if it fails.

This adds a new function, run_command_silent_on_success(), to
redirect the stdout and stderr of a command to a strbuf, and then to run
that command. This strbuf is printed only if the command fails. It is
functionnaly similar to output() from git-rebase.sh.

run_git_commit() is then refactored to use of
run_command_silent_on_success().

Signed-off-by: Alban Gruin <redacted>
---
 sequencer.c | 49 ++++++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 57fd58bc1..9e2b34a49 100644
--- a/sequencer.c
+++ b/sequencer.c

@@ -768,6 +768,24 @@ N_("you have staged changes in your working tree\n"
 #define VERIFY_MSG  (1<<4)
 #define CREATE_ROOT_COMMIT (1<<5)
 
+static int run_command_silent_on_success(struct child_process *cmd)
+{
+	struct strbuf buf = STRBUF_INIT;
+	int rc;
+
+	cmd->stdout_to_stderr = 1;
+	rc = pipe_command(cmd,
+			  NULL, 0,
+			  /* stdout is already redirected */