libgit2 0.22.1和v0.21.5维护版本发布

libgit2 今天发布两个维护版本，分别是 0.22.1 和 0.21.5。这两个版本的改进记录包括：

0.22.1：

• bd0e881 checkout: introduce git_checkout_perfdata

• 1ca7fa9 git_path_join_unrooted: return base len

• 9f1c873 checkout: don't recreate previous directory

• 99367df checkout tests: nasty symlinks

• b295294 checkout: drop newline in error message

• 8d65523 checkout: remove files before writing new ones

• f9df7b6 checkout tests: emulate p_realpath poorly on Win32

• 1ce9ea3 checkout tests: cleanup realpath impl on Win32

0.21.5：

• af769f4 checkout: introduce git_checkout_perfdata

• fc478d2 git_path_join_unrooted: return base len

• 629a579 checkout: don't recreate previous directory

• dd3c53f checkout tests: nasty symlinks

• 186177a checkout: drop newline in error message

• 7268a5a checkout: remove files before writing new ones

• e517b62 checkout tests: emulate p_realpath poorly on Win32

• 9a8753d checkout tests: cleanup realpath impl on Win32

• 8433078 Introduce test for checkout case-changing rename

• d853fb9 Always checkout with case sensitive iterator