use write_file_buf where applicable

There are several places where we open a file, write some
content from a strbuf, and close it. These can be simplified
with write_file_buf(). As a bonus, many of these did not
catch write problems at close() time.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/am.c

@@ -402,13 +402,8 @@ static int read_commit_msg(struct am_state *state)
  */
 static void write_commit_msg(const struct am_state *state)
 {
-	int fd;
 	const char *filename = am_path(state, "final-commit");
-
-	fd = xopen(filename, O_WRONLY | O_CREAT, 0666);
-	if (write_in_full(fd, state->msg, state->msg_len) < 0)
-		die_errno(_("could not write to %s"), filename);
-	close(fd);
+	write_file_buf(filename, state->msg, state->msg_len);
 }
 
 /**

builtin/merge.c

@@ -336,15 +336,9 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
 	struct rev_info rev;
 	struct strbuf out = STRBUF_INIT;
 	struct commit_list *j;
-	const char *filename;
-	int fd;
 	struct pretty_print_context ctx = {0};
 
 	printf(_("Squash commit -- not updating HEAD\n"));
-	filename = git_path_squash_msg();
-	fd = open(filename, O_WRONLY | O_CREAT, 0666);
-	if (fd < 0)
-		die_errno(_("Could not write to '%s'"), filename);
 
 	init_revisions(&rev, NULL);
 	rev.ignore_merges = 1;
@@ -371,10 +365,7 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
 			oid_to_hex(&commit->object.oid));
 		pretty_print_commit(&ctx, commit, &out);
 	}
-	if (write_in_full(fd, out.buf, out.len) != out.len)
-		die_errno(_("Writing SQUASH_MSG"));
-	if (close(fd))
-		die_errno(_("Finishing SQUASH_MSG"));
+	write_file_buf(git_path_squash_msg(), out.buf, out.len);
 	strbuf_release(&out);
 }
 
@@ -756,18 +747,6 @@ static void add_strategies(const char *string, unsigned attr)
 
 }
 
-static void write_merge_msg(struct strbuf *msg)
-{
-	const char *filename = git_path_merge_msg();
-	int fd = open(filename, O_WRONLY | O_CREAT, 0666);
-	if (fd < 0)
-		die_errno(_("Could not open '%s' for writing"),
-			  filename);
-	if (write_in_full(fd, msg->buf, msg->len) != msg->len)
-		die_errno(_("Could not write to '%s'"), filename);
-	close(fd);
-}
-
 static void read_merge_msg(struct strbuf *msg)
 {
 	const char *filename = git_path_merge_msg();
@@ -801,7 +780,7 @@ static void prepare_to_commit(struct commit_list *remoteheads)
 	strbuf_addch(&msg, '\n');
 	if (0 < option_edit)
 		strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
-	write_merge_msg(&msg);
+	write_file_buf(git_path_merge_msg(), msg.buf, msg.len);
 	if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 			    git_path_merge_msg(), "merge", NULL))
 		abort_commit(remoteheads, NULL);
@@ -964,8 +943,6 @@ static int setup_with_upstream(const char ***argv)
 
 static void write_merge_state(struct commit_list *remoteheads)
 {
-	const char *filename;
-	int fd;
 	struct commit_list *j;
 	struct strbuf buf = STRBUF_INIT;
 
@@ -979,26 +956,14 @@ static void write_merge_state(struct commit_list *remoteheads)
 		}
 		strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 	}
-	filename = git_path_merge_head();
-	fd = open(filename, O_WRONLY | O_CREAT, 0666);
-	if (fd < 0)
-		die_errno(_("Could not open '%s' for writing"), filename);
-	if (write_in_full(fd, buf.buf, buf.len) != buf.len)
-		die_errno(_("Could not write to '%s'"), filename);
-	close(fd);
+	write_file_buf(git_path_merge_head(), buf.buf, buf.len);
 	strbuf_addch(&merge_msg, '\n');
-	write_merge_msg(&merge_msg);
+	write_file_buf(git_path_merge_msg(), merge_msg.buf, merge_msg.len);
 
-	filename = git_path_merge_mode();
-	fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
-	if (fd < 0)
-		die_errno(_("Could not open '%s' for writing"), filename);
 	strbuf_reset(&buf);
 	if (fast_forward == FF_NO)
 		strbuf_addf(&buf, "no-ff");
-	if (write_in_full(fd, buf.buf, buf.len) != buf.len)
-		die_errno(_("Could not write to '%s'"), filename);
-	close(fd);
+	write_file_buf(git_path_merge_mode(), buf.buf, buf.len);
 }
 
 static int default_edit_option(void)