ash: match behaviour of cmd.exe in cd builtin

The Windows API strips trailing dots and spaces from the last
component of a path.  cmd.exe handles this quirk when changing
directory by adjusting its idea of the current directory to match
reality.  The shell in busybox-w32 didn't do this, leading to some
confusion.

Fix the shell's cd builtin so it works more like cmd.exe.

Adds 64-80 bytes.

(GitHub issue #478)

3 files changed, 15 insertions, 0 deletions

diff --git a/include/mingw.h b/include/mingw.h
index 5a3c75ff6..c41c0f91e 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -631,6 +631,7 @@ MINGW_BB_WCHAR_T *bs_to_slash_u(MINGW_BB_WCHAR_T *p) FAST_FUNC;
 
 char *bs_to_slash(char *p) FAST_FUNC;
 void slash_to_bs(char *p) FAST_FUNC;
+void strip_dot_space(char *p) FAST_FUNC;
 size_t remove_cr(char *p, size_t len) FAST_FUNC;
 
 int err_win_to_posix(void);
diff --git a/shell/ash.c b/shell/ash.c
index 1fc2a44b1..3919118f0 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -3338,6 +3338,7 @@ updatepwd(const char *dir)
         if (new > lim)
                 STUNPUTC(new);
         *new = 0;
+        strip_dot_space((char *)stackblock());
         fix_path_case((char *)stackblock());
         return bs_to_slash((char *)stackblock());
 #else
diff --git a/win32/mingw.c b/win32/mingw.c
index 87e7ca602..6842dba48 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -2178,6 +2178,19 @@ void FAST_FUNC slash_to_bs(char *p)
         }
 }
 
+/* Windows strips trailing dots and spaces from the last component of
+ * a file path.  This routine emulates that behaviour so we can preempt
+ * Windows if necessary. */
+void FAST_FUNC strip_dot_space(char *p)
+{
+        char *start = (char *)bb_basename(p);
+        char *end = start + strlen(start);
+
+        while (end > start && (end[-1] == '.' || end[-1] == ' ')) {
+                *--end = '\0';
+        }
+}
+
 size_t FAST_FUNC remove_cr(char *p, size_t len)
 {
         ssize_t i, j;