do not let git_path clobber errno when reporting errors

Because git_path() calls vsnprintf(), code like

	fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
	die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));

can end up printing an error indicator from vsnprintf() instead of
open() by mistake.  Store the path we are trying to write to in a
temporary variable and pass _that_ to die_errno(), so the messages
written by git cherry-pick/revert and git merge can avoid this source
of confusion.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/builtin/revert.c b/builtin/revert.c
index b61c8e5c52..544e8c3057 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -288,17 +288,18 @@ static char *get_encoding(const char *message)
 
 static void write_cherry_pick_head(struct commit *commit)
 {
+	const char *filename;
 	int fd;
 	struct strbuf buf = STRBUF_INIT;
 
 	strbuf_addf(&buf, "%s\n", sha1_to_hex(commit->object.sha1));
 
-	fd = open(git_path("CHERRY_PICK_HEAD"), O_WRONLY | O_CREAT, 0666);
+	filename = git_path("CHERRY_PICK_HEAD");
+	fd = open(filename, O_WRONLY | O_CREAT, 0666);
 	if (fd < 0)
-		die_errno(_("Could not open '%s' for writing"),
-			  git_path("CHERRY_PICK_HEAD"));
+		die_errno(_("Could not open '%s' for writing"), filename);
 	if (write_in_full(fd, buf.buf, buf.len) != buf.len || close(fd))
-		die_errno(_("Could not write to '%s'"), git_path("CHERRY_PICK_HEAD"));
+		die_errno(_("Could not write to '%s'"), filename);
 	strbuf_release(&buf);
 }