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, 3 insertions, 0 deletions

diff --git a/include/mingw.h b/include/mingw.h
index 6ace91470..06fb3b289 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -518,6 +518,8 @@ int utimes(const char *file_name, const struct timeval times[2]);
  * MinGW specific
  */
 #define is_dir_sep(c) ((c) == '/' || (c) == '\\')
+#define is_unc_path(x) (strlen(x) > 4 && is_dir_sep(x[0]) && \
+                                                        is_dir_sep(x[1]) && !is_dir_sep(x[2]))
 
 pid_t FAST_FUNC mingw_spawn(char **argv);
 pid_t FAST_FUNC mingw_spawn_detach(char **argv);
@@ -580,3 +582,4 @@ int skip_ansi_emulation(int reset);
 int unix_path(const char *path);
 int has_path(const char *file);
 int is_relative_path(const char *path);
+char *get_last_slash(const char *path);