patch 8.0.1553: cannot see what digraph is used to insert a character

Problem:    Cannot see what digraph is used to insert a character.
Solution:   Show the digraph with the "ga" command. (Christian Brabandt)

src/digraph.c

@@ -1974,6 +1974,41 @@ do_digraph(int c)
     return c;
 }
 
+/*
+ * Find a digraph for "val".  If found return the string to display it.
+ * If not found return NULL.
+ */
+    char_u *
+get_digraph_for_char(val)
+    int val;
+{
+    int		i;
+    int		use_defaults;
+    digr_T	*dp;
+    static      char_u      r[3];
+
+    for (use_defaults = 0; use_defaults <= 1; use_defaults++)
+    {
+	if (use_defaults == 0)
+	    dp = (digr_T *)user_digraphs.ga_data;
+	else
+	    dp = digraphdefault;
+	for (i = 0; use_defaults ? dp->char1 != NUL
+					       : i < user_digraphs.ga_len; ++i)
+	{
+	    if (dp->result == val)
+	    {
+		r[0] = dp->char1;
+		r[1] = dp->char2;
+		r[2] = NUL;
+		return r;
+	    }
+	    ++dp;
+	}
+    }
+    return NULL;
+}
+
 /*
  * Get a digraph.  Used after typing CTRL-K on the command line or in normal
  * mode.