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, 12 insertions, 0 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 1d5644f92..ec7d6c456 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1700,3 +1700,15 @@ char *xabsolute_path(char *path)
         }
         bb_perror_msg_and_die("can't open '%s'", path);
 }
+
+char *get_drive_cwd(const char *path, char *buffer, int size)
+{
+        char drive[3] = { *path, ':', '\0' };
+        DWORD ret;
+
+        ret = GetFullPathName(drive, size, buffer, NULL);
+        if (ret == 0 || ret > size)
+                return NULL;
+        bs_to_slash(buffer);
+        return buffer;
+}