interpret-trailers: refactor create_in_place_tempfile()

Refactor create_in_place_tempfile() in preparation for moving it
to tralier.c. Change the return type to return a `struct tempfile*`
instead of a `FILE*` so that we can remove the file scope tempfile
variable. Since 076aa2c (tempfile: auto-allocate tempfiles on
heap, 2017-09-05) it has not been necessary to make tempfile varibales
static so this is safe. Also use error() and return NULL in place of
die() so the caller can exit gracefully and use find_last_dir_sep()
rather than strchr() to find the parent directory.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: phillipwood

builtin/interpret-trailers.c

@@ -93,35 +93,37 @@ static int parse_opt_parse(const struct option *opt, const char *arg,
 	return 0;
 }
 
-static struct tempfile *trailers_tempfile;
 
-static FILE *create_in_place_tempfile(const char *file)
+static struct tempfile *create_in_place_tempfile(const char *file)
 {
+	struct tempfile *tempfile = NULL;
 	struct stat st;
 	struct strbuf filename_template = STRBUF_INIT;
 	const char *tail;
-	FILE *outfile;
-
-	if (stat(file, &st))
-		die_errno(_("could not stat %s"), file);
-	if (!S_ISREG(st.st_mode))
-		die(_("file %s is not a regular file"), file);
-	if (!(st.st_mode & S_IWUSR))
-		die(_("file %s is not writable by user"), file);
 
+	if (stat(file, &st)) {
+		error_errno(_("could not stat %s"), file);
+		return NULL;
+	}
+	if (!S_ISREG(st.st_mode)) {
+		error(_("file %s is not a regular file"), file);
+		return NULL;
+	}
+	if (!(st.st_mode & S_IWUSR)) {
+		error(_("file %s is not writable by user"), file);
+		return NULL;
+	}
 	/* Create temporary file in the same directory as the original */
-	tail = strrchr(file, '/');
+	tail = find_last_dir_sep(file);
 	if (tail)
 		strbuf_add(&filename_template, file, tail - file + 1);
 	strbuf_addstr(&filename_template, "git-interpret-trailers-XXXXXX");
 
-	trailers_tempfile = xmks_tempfile_m(filename_template.buf, st.st_mode);
+	tempfile = mks_tempfile_m(filename_template.buf, st.st_mode);
+
 	strbuf_release(&filename_template);
-	outfile = fdopen_tempfile(trailers_tempfile, "w");
-	if (!outfile)
-		die_errno(_("could not open temporary file"));
 
-	return outfile;
+	return tempfile;
 }
 
 static void read_input_file(struct strbuf *sb, const char *file)
@@ -178,20 +180,25 @@ static void interpret_trailers(const struct process_trailer_options *opts,
 {
 	struct strbuf input = STRBUF_INIT;
 	struct strbuf out = STRBUF_INIT;
-	FILE *outfile = stdout;
+	struct tempfile *tempfile = NULL;
+	int fd = 1;
 
 	trailer_config_init();
 
 	read_input_file(&input, file);
 
-	if (opts->in_place)
-		outfile = create_in_place_tempfile(file);
-
+	if (opts->in_place) {
+		tempfile = create_in_place_tempfile(file);
+		if (!tempfile)
+			die(NULL);
+		fd = tempfile->fd;
+	}
 	process_trailers(opts, new_trailer_head, &input, &out);
 
-	strbuf_write(&out, outfile);
+	if (write_in_full(fd, out.buf, out.len) < 0)
+		die_errno(_("could not write to temporary file '%s'"), file);
 	if (opts->in_place)
-		if (rename_tempfile(&trailers_tempfile, file))
+		if (rename_tempfile(&tempfile, file))
 			die_errno(_("could not rename temporary file to %s"), file);
 
 	strbuf_release(&input);