detect close failure on just-written file handles

I audited git for potential undetected write failures.
In the cases fixed below, the diagnostics I add mimic the diagnostics
used in surrounding code, even when that means not reporting
the precise strerror(errno) cause of the error.

Signed-off-by: Jim Meyering <jim@meyering.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-init-db.c

@@ -40,7 +40,8 @@ static int copy_file(const char *dst, const char *src, int mode)
 		return fdo;
 	}
 	status = copy_fd(fdi, fdo);
-	close(fdo);
+	if (close(fdo) != 0)
+		return error("%s: write error: %s", dst, strerror(errno));
 
 	if (!status && adjust_shared_perm(dst))
 		return -1;

builtin-rerere.c

@@ -57,7 +57,8 @@ static int write_rr(struct path_list *rr, int out_fd)
 		    write_in_full(out_fd, path, length) != length)
 			die("unable to write rerere record");
 	}
-	close(out_fd);
+	if (close(out_fd) != 0)
+		die("unable to write rerere record");
 	return commit_lock_file(&write_lock);
 }
 

index-pack.c

@@ -634,7 +634,8 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 				write_or_die(keep_fd, keep_msg, keep_msg_len);
 				write_or_die(keep_fd, "\n", 1);
 			}
-			close(keep_fd);
+			if (close(keep_fd) != 0)
+				die("cannot write keep file");
 			report = "keep";
 		}
 	}

refs.c

@@ -1106,8 +1106,7 @@ static int log_ref_write(const char *ref_name, const unsigned char *old_sha1,
 		len += sprintf(logrec + len - 1, "\t%.*s\n", msglen, msg) - 1;
 	written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
 	free(logrec);
-	close(logfd);
-	if (written != len)
+	if (close(logfd) != 0 || written != len)
 		return error("Unable to append to %s", log_file);
 	return 0;
 }
@@ -1204,8 +1203,7 @@ int create_symref(const char *ref_target, const char *refs_heads_master,
 		goto error_free_return;
 	}
 	written = write_in_full(fd, ref, len);
-	close(fd);
-	if (written != len) {
+	if (close(fd) != 0 || written != len) {
 		error("Unable to write to %s", lockpath);
 		goto error_unlink_return;
 	}