commit: don't be fooled by ita entries when creating initial commit

ita entries are dropped at tree generation phase. If the entire index
consists of just ita entries, the result would be a a commit with no
entries, which should be caught unless --allow-empty is specified. The
test "!!active_nr" is not sufficient to catch this.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit.c b/builtin/commit.c
index 400d2a5..1e74bc1 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -894,9 +894,14 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		if (amend)
 			parent = "HEAD^1";
 
-		if (get_sha1(parent, sha1))
-			commitable = !!active_nr;
-		else {
+		if (get_sha1(parent, sha1)) {
+			int i, ita_nr = 0;
+
+			for (i = 0; i < active_nr; i++)
+				if (ce_intent_to_add(active_cache[i]))
+					ita_nr++;
+			commitable = active_nr - ita_nr > 0;
+		} else {
 			/*
 			 * Unless the user did explicitly request a submodule
 			 * ignore mode by passing a command line option we do