realpath: improved support for Windows paths

Upstream commit 94eb1c4dc (libbb: better coreutils compatibility
for realpath) made some changes to xmalloc_realpath_coreutils().
This now needs to be updated to handle Windows paths.

- Expose the macro is_unc_path() and part of the recent change to
  bb_get_last_path_component_nostrip() as a separate funtion,
  get_last_slash();

- Convert a couple of errors relating to network filesystems to
  ENOENT;

- Adjust xmalloc_realpath_coreutils() to handle Windows directory
  separators, relative paths and UNC paths.

1 files changed, 2 insertions, 3 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index fa68ea608..d4855a7e7 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -64,6 +64,8 @@ int err_win_to_posix(void)
         case ERROR_BAD_FORMAT: error = ENOEXEC; break;
         case ERROR_BAD_LENGTH: error = EINVAL; break;
         case ERROR_BAD_PATHNAME: error = ENOENT; break;
+        case ERROR_BAD_NET_NAME: error = ENOENT; break;
+        case ERROR_BAD_NETPATH: error = ENOENT; break;
         case ERROR_BAD_PIPE: error = EPIPE; break;
         case ERROR_BAD_UNIT: error = ENODEV; break;
         case ERROR_BAD_USERNAME: error = EINVAL; break;
@@ -1877,9 +1879,6 @@ void hide_console(void)
 }
 #endif
 
-#define is_unc_path(x) (strlen(x) > 4 && is_dir_sep(x[0]) && \
-                                                        is_dir_sep(x[1]) && !is_dir_sep(x[2]))
-
 /* Return the length of the root of a UNC path, i.e. the '//host/share'
  * component, or 0 if the path doesn't look like that. */
 int unc_root_len(const char *dir)