pathspec: remove PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE flag

Since (ae8d08242 pathspec: pass directory indicator to
match_pathspec_item()) the path matching logic has been able to cope
with submodules without needing to strip off a trailing slash if a path
refers to a submodule.

Since the stripping the trailing slash is no longer necessary, remove
the PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE flag.  In addition, factor
out the logic which dies if a path decends into a submodule so that it
can still be used as a check after a pathspec struct has been
initialized.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

submodule.c

@@ -312,6 +312,39 @@ void die_in_unpopulated_submodule(const struct index_state *istate,
 	}
 }
 
+/*
+ * Dies if any paths in the provided pathspec descends into a submodule
+ */
+void die_path_inside_submodule(const struct index_state *istate,
+			       const struct pathspec *ps)
+{
+	int i, j;
+
+	for (i = 0; i < istate->cache_nr; i++) {
+		struct cache_entry *ce = istate->cache[i];
+		int ce_len = ce_namelen(ce);
+
+		if (!S_ISGITLINK(ce->ce_mode))
+			continue;
+
+		for (j = 0; j < ps->nr ; j++) {
+			const struct pathspec_item *item = &ps->items[j];
+
+			if (item->len <= ce_len)
+				continue;
+			if (item->match[ce_len] != '/')
+				continue;
+			if (strncmp(ce->name, item->match, ce_len))
+				continue;
+			if (item->len == ce_len + 1)
+				continue;
+
+			die(_("Pathspec '%s' is in submodule '%.*s'"),
+			    item->original, ce_len, ce->name);
+		}
+	}
+}
+
 int parse_submodule_update_strategy(const char *value,
 		struct submodule_update_strategy *dst)
 {