+static const char post_rewrite_hook[] = "hooks/post-rewrite";
+
+static int run_rewrite_hook(const unsigned char *oldsha1,
+ const unsigned char *newsha1)
+{
+ /* oldsha1 SP newsha1 LF NUL */
+ static char buf[2*40 + 3];
+ struct child_process proc;
+ const char *argv[3];
+ int code;
+ size_t n;
+
+ if (access(git_path(post_rewrite_hook), X_OK) < 0)
+ return 0;
+
+ argv[0] = git_path(post_rewrite_hook);
+ argv[1] = "amend";
+ argv[2] = NULL;
+
+ memset(&proc, 0, sizeof(proc));
+ proc.argv = argv;
+ proc.in = -1;
+ proc.stdout_to_stderr = 1;
+
+ code = start_command(&proc);
+ if (code)
+ return code;
+ n = snprintf(buf, sizeof(buf), "%s %s\n",
+ sha1_to_hex(oldsha1), sha1_to_hex(newsha1));
+ write_in_full(proc.in, buf, n);
+ close(proc.in);
+ return finish_command(&proc);
+}
+