Nicer error messages in case saving an object to db goes wrong

Currently the error e.g. when pushing to a read-only repository is quite
confusing, this attempts to clean it up, unifies error reporting between
various object writers and uses error() on couple more places.

Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>

sha1_file.c

@@ -1420,8 +1420,7 @@ int move_temp_to_file(const char *tmpfile, const char *filename)
 	unlink(tmpfile);
 	if (ret) {
 		if (ret != EEXIST) {
-			fprintf(stderr, "unable to write sha1 filename %s: %s\n", filename, strerror(ret));
-			return -1;
+			return error("unable to write sha1 filename %s: %s\n", filename, strerror(ret));
 		}
 		/* FIXME!!! Collision check here ? */
 	}
@@ -1531,16 +1530,17 @@ int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned cha
 	}
 
 	if (errno != ENOENT) {
-		fprintf(stderr, "sha1 file %s: %s\n", filename, strerror(errno));
-		return -1;
+		return error("sha1 file %s: %s\n", filename, strerror(errno));
 	}
 
 	snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
 
 	fd = mkstemp(tmpfile);
 	if (fd < 0) {
-		fprintf(stderr, "unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
-		return -1;
+		if (errno == EPERM)
+			return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());
+		else
+			return error("unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
 	}
 
 	/* Set it up */
@@ -1655,9 +1655,12 @@ int write_sha1_from_fd(const unsigned char *sha1, int fd, char *buffer,
 	snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
 
 	local = mkstemp(tmpfile);
-	if (local < 0)
-		return error("Couldn't open %s for %s",
-			     tmpfile, sha1_to_hex(sha1));
+	if (local < 0) {
+		if (errno == EPERM)
+			return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());
+		else
+			return error("unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
+	}
 
 	memset(&stream, 0, sizeof(stream));