win32: improved support for c:path path names

Microsoft Windows permits path names of the form 'c:path', without a
path separator after the colon.  The system records a current directory
for each drive and the path is interpreted relative to that.

Since Windows API calls understand 'c:path' path names many commands
in busybox-w32 already work with them.  This commit adds the following:

- The 'cd' shell built-in interprets 'c:path' path names correctly.
  Previously it treated them as relative to the shell's concept of
  the current working directory, not the current directory of the
  specified drive.

- The 'pwd' shell built-in takes the '-a' option to list the current
  directory for all drives.

- 'c:path' path names are subject to tab-completion.

Paths of the form 'c:path' don't work for mapped network drives or
paths that have been associated with a drive using SUBST.

See GitHub issue #147.

1 files changed, 1 insertions, 0 deletions

diff --git a/include/mingw.h b/include/mingw.h
index d77a9beb9..8b295814c 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -528,3 +528,4 @@ int root_len(const char *path);
 char *get_system_drive(void);
 int chdir_system_drive(void);
 char *xabsolute_path(char *path);
+char *get_drive_cwd(const char *path, char *buffer, int size);