Merge branch 'ld/discovery-limit-to-fs' (early part)

* 'ld/discovery-limit-to-fs' (early part):
  Rename ONE_FILESYSTEM to DISCOVERY_ACROSS_FILESYSTEM
  GIT_ONE_FILESYSTEM: flip the default to stop at filesystem boundaries
  Add support for GIT_ONE_FILESYSTEM
  truncate cwd string before printing error message
  config.c: remove static keyword from git_env_bool()

config.c

@@ -739,7 +739,7 @@ const char *git_etc_gitconfig(void)
 	return system_wide;
 }
 
-static int git_env_bool(const char *k, int def)
+int git_env_bool(const char *k, int def)
 {
 	const char *v = getenv(k);
 	return v ? git_config_bool(k, v) : def;