fix failure of glob to match broken symlinks under some conditions

when the pattern ended with one or more literal path components, or
when the GLOB_MARK flag was passed to request that glob flag directory
results and the type obtained by readdir was unknown or inconclusive
(symlink), the stat function was called to evaluate existence and/or
determine type. however, stat fails with ENOENT for broken symlinks,
and this caused the match to be omitted from the results.

instead, use stat only for the unknown/inconclusive cases with
GLOB_MARK, and otherwise, or if stat fails, use lstat existence still
needs to be determined. this minimizes the number of costly syscalls,
performing both only in the case where GLOB_MARK is in use and there
is a final literal path component which is a broken symlink.

based on/simplified from patch by James Y Knight.

src/regex/glob.c

@@ -92,16 +92,23 @@ static int do_glob(char *buf, size_t pos, int type, char *pat, int flags, int (*
 	if (!*pat) {
 		/* If we consumed any components above, or if GLOB_MARK is
 		 * requested and we don't yet know if the match is a dir,
-		 * we must call stat to confirm the file exists and/or
-		 * determine its type. */
+		 * we must confirm the file exists and/or determine its type.
+		 *
+		 * If marking dirs, symlink type is inconclusive; we need the
+		 * type for the symlink target, and therefore must try stat
+		 * first unless type is known not to be a symlink. Otherwise,
+		 * or if that fails, use lstat for determining existence to
+		 * avoid false negatives in the case of broken symlinks. */
 		struct stat st;
-		if ((flags & GLOB_MARK) && type==DT_LNK) type = 0;
-		if (!type && stat(buf, &st)) {
+		if ((flags & GLOB_MARK) && (!type||type==DT_LNK) && !stat(buf, &st)) {
+			if (S_ISDIR(st.st_mode)) type = DT_DIR;
+			else type = DT_REG;
+		}
+		if (!type && lstat(buf, &st)) {
 			if (errno!=ENOENT && (errfunc(buf, errno) || (flags & GLOB_ERR)))
 				return GLOB_ABORTED;
 			return 0;
 		}
-		if (!type && S_ISDIR(st.st_mode)) type = DT_DIR;
 		if (append(tail, buf, pos, (flags & GLOB_MARK) && type==DT_DIR))
 			return GLOB_NOSPACE;
 		return 0;