Subject: [PATCH v4 08/29] trailer: handle trailer append failures gently

From: Li Chen <[email-masked]>
Date: Tue, 14 Oct 2025 20:24:21 +0800

Added write_file_buf_gently so callers can rewrite
files while surfacing errors instead of aborting.

Updated amend_file_with_trailers to release buffers
and propagate trailer and write failures back to the caller,
because amend_file_with_trailers shuold not die.

Signed-off-by: Li Chen <[email-masked]>
---
 trailer.c | 14 ++++++++++----
 wrapper.c | 16 ++++++++++++++++
 wrapper.h |  6 ++++++
 3 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/trailer.c b/trailer.c
index 5329589064..b0ad7dc5c3 100644
--- a/trailer.c
+++ b/trailer.c
@@ -9,6 +9,7 @@
 #include "commit.h"
 #include "trailer.h"
 #include "list.h"
+#include "wrapper.h"
 /*
  * Copyright (c) 2013, 2014 Christian Couder <[email-masked]>
  */
@@ -1308,11 +1309,16 @@ int amend_file_with_trailers(const char *path,
 	if (strbuf_read_file(&buf, path, 0) < 0)
 		return error_errno("could not read '%s'", path);
 
-	if (amend_strbuf_with_trailers(&buf, trailer_args))
-		die("failed to append trailers");
+	if (amend_strbuf_with_trailers(&buf, trailer_args)) {
+		strbuf_release(&buf);
+		return error("failed to append trailers");
+	}
+
+	if (write_file_buf_gently(path, buf.buf, buf.len)) {
+		strbuf_release(&buf);
+		return -1;
+	}
 
-	/* `write_file_buf()` aborts on error internally */
-	write_file_buf(path, buf.buf, buf.len);
 	strbuf_release(&buf);
 	return 0;
 }
diff --git a/wrapper.c b/wrapper.c
index 2f00d2ac87..2aeba8b049 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -688,6 +688,22 @@ void write_file_buf(const char *path, const char *buf, size_t len)
 		die_errno(_("could not close '%s'"), path);
 }
 
+int write_file_buf_gently(const char *path, const char *buf, size_t len)
+{
+	int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0666);
+
+	if (fd < 0)
+		return error_errno(_("could not open '%s'"), path);
+	if (write_in_full(fd, buf, len) < 0) {
+		int ret = error_errno(_("could not write to '%s'"), path);
+		close(fd);
+		return ret;
+	}
+	if (close(fd))
+		return error_errno(_("could not close '%s'"), path);
+	return 0;
+}
+
 void write_file(const char *path, const char *fmt, ...)
 {
 	va_list params;
diff --git a/wrapper.h b/wrapper.h
index 7df824e34a..5b7d7a78fb 100644
--- a/wrapper.h
+++ b/wrapper.h
@@ -56,6 +56,12 @@ static inline ssize_t write_str_in_full(int fd, const char *str)
  */
 void write_file_buf(const char *path, const char *buf, size_t len);
 
+/**
+ * Like write_file_buf(), but report errors instead of exiting. Returns 0 on
+ * success or a negative value on error after emitting a message.
+ */
+int write_file_buf_gently(const char *path, const char *buf, size_t len);
+
 /**
  * Like write_file_buf(), but format the contents into a buffer first.
  * Additionally, write_file() will append a newline if one is not already
-- 
2.51.0