userdiff.c: add builtin fortran regex patterns

This adds fortran xfuncname and wordRegex patterns to the list of builtin
patterns.  The intention is for the patterns to be appropriate for all
versions of fortran including 77, 90, 95.  The patterns can be enabled by
adding the diff=fortran attribute to the .gitattributes file for the
desired file glob.

This also adds a new macro named IPATTERN which is just like the PATTERNS
macro except it sets the REG_ICASE flag so that case will be ignored.

The test code in t4018 and the docs were updated as appropriate.

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitattributes.txt

@@ -477,6 +477,8 @@ patterns are available:
 
 - `csharp` suitable for source code in the C# language.
 
+- `fortran` suitable for source code in the Fortran language.
+
 - `html` suitable for HTML/XHTML documents.
 
 - `java` suitable for source code in the Java language.

t/t4018-diff-funcname.sh

@@ -32,7 +32,7 @@ EOF
 
 sed 's/beer\\/beer,\\/' < Beer.java > Beer-correct.java
 
-builtin_patterns="bibtex cpp csharp html java objc pascal php python ruby tex"
+builtin_patterns="bibtex cpp csharp fortran html java objc pascal php python ruby tex"
 for p in $builtin_patterns
 do
 	test_expect_success "builtin $p pattern compiles" '

userdiff.c

@@ -9,7 +9,23 @@ static int drivers_alloc;
 
 #define PATTERNS(name, pattern, word_regex)			\
 	{ name, NULL, -1, { pattern, REG_EXTENDED }, word_regex }
+#define IPATTERN(name, pattern, word_regex)			\
+	{ name, NULL, -1, { pattern, REG_EXTENDED | REG_ICASE }, word_regex }
 static struct userdiff_driver builtin_drivers[] = {
+IPATTERN("fortran",
+	 "!^([C*]|[ \t]*!)\n"
+	 "!^[ \t]*MODULE[ \t]+PROCEDURE[ \t]\n"
+	 "^[ \t]*((END[ \t]+)?(PROGRAM|MODULE|BLOCK[ \t]+DATA"
+		"|([^'\" \t]+[ \t]+)*(SUBROUTINE|FUNCTION))[ \t]+[A-Z].*)$",
+	 /* -- */
+	 "[a-zA-Z][a-zA-Z0-9_]*"
+	 "|\\.([Ee][Qq]|[Nn][Ee]|[Gg][TtEe]|[Ll][TtEe]|[Tt][Rr][Uu][Ee]|[Ff][Aa][Ll][Ss][Ee]|[Aa][Nn][Dd]|[Oo][Rr]|[Nn]?[Ee][Qq][Vv]|[Nn][Oo][Tt])\\."
+	 /* numbers and format statements like 2E14.4, or ES12.6, 9X.
+	  * Don't worry about format statements without leading digits since
+	  * they would have been matched above as a variable anyway. */
+	 "|[-+]?[0-9.]+([AaIiDdEeFfLlTtXx][Ss]?[-+]?[0-9.]*)?(_[a-zA-Z0-9][a-zA-Z0-9_]*)?"
+	 "|//|\\*\\*|::|[/<>=]="
+	 "|[^[:space:]]|[\x80-\xff]+"),
 PATTERNS("html", "^[ \t]*(<[Hh][1-6][ \t].*>.*)$",
 	 "[^<>= \t]+|[^[:space:]]|[\x80-\xff]+"),
 PATTERNS("java",
@@ -101,6 +117,7 @@ PATTERNS("csharp",
 { "default", NULL, -1, { NULL, 0 } },
 };
 #undef PATTERNS
+#undef IPATTERN
 
 static struct userdiff_driver driver_true = {
 	"diff=true",