userdiff: fix some corner cases in dts regex

While reviewing some dts diffs recently I noticed that the hunk header
logic was failing to find the containing node. This is because the regex
doesn't consider properties that may span multiple lines, i.e.

	property = <something>,
		   <something_else>;

and it got hung up on comments inside nodes that look like the root node
because they start with '/*'. Add tests for these cases and update the
regex to find them. Maybe detecting the root node is too complicated but
forcing it to be a backslash with any amount of whitespace up to an open
bracket seemed OK. I tried to detect that a comment is in-between the
two parts but I wasn't happy so I just dropped it.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/userdiff.c b/userdiff.c
index 86e3244..e187d35 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -25,8 +25,9 @@ IPATTERN("ada",
 	 "|=>|\\.\\.|\\*\\*|:=|/=|>=|<=|<<|>>|<>"),
 PATTERNS("dts",
 	 "!;\n"
+	 "!=\n"
 	 /* lines beginning with a word optionally preceded by '&' or the root */
-	 "^[ \t]*((/|&?[a-zA-Z_]).*)",
+	 "^[ \t]*((/[ \t]*\\{|&?[a-zA-Z_]).*)",
 	 /* -- */
 	 /* Property names and math operators */
 	 "[a-zA-Z0-9,._+?#-]+"