Use compatibility regex library for OSX/Darwin

The standard libc regex library on OSX does not support alternation
in POSIX Basic Regular Expression mode.  This breaks the diff.funcname
functionality on OSX.

To fix this, we use the GNU regex library which is already present in
the compat/ diretory for the MinGW port.  However, simply adding compat/
to the COMPAT_CFLAGS variable causes a conflict between the system
fnmatch.h and the one present in compat/.  To remedy this, move the
regex and fnmatch functionality to their own subdirectories in compat/
so they can be included seperately.

Signed-off-by: Arjen Laarhoven <arjen@yaph.org>
Tested-by: Mike Ralphson <mike@abacus.co.uk> (AIX)
Tested-by: Johannes Sixt <johannes.sixt@telecom.at> (MinGW)
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -626,6 +626,8 @@ ifeq ($(uname_S),Darwin)
 	endif
 	NO_STRLCPY = YesPlease
 	NO_MEMMEM = YesPlease
+	COMPAT_CFLAGS += -Icompat/regex
+	COMPAT_OBJS += compat/regex/regex.o
 endif
 ifeq ($(uname_S),SunOS)
 	NEEDS_SOCKET = YesPlease
@@ -750,10 +752,10 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_SVN_TESTS = YesPlease
 	NO_PERL_MAKEMAKER = YesPlease
 	NO_POSIX_ONLY_PROGRAMS = YesPlease
-	COMPAT_CFLAGS += -D__USE_MINGW_ACCESS -DNOGDI -Icompat
+	COMPAT_CFLAGS += -D__USE_MINGW_ACCESS -DNOGDI -Icompat -Icompat/regex -Icompat/fnmatch
 	COMPAT_CFLAGS += -DSNPRINTF_SIZE_CORR=1
 	COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"
-	COMPAT_OBJS += compat/mingw.o compat/fnmatch.o compat/regex.o compat/winansi.o
+	COMPAT_OBJS += compat/mingw.o compat/fnmatch/fnmatch.o compat/regex/regex.o compat/winansi.o
 	EXTLIBS += -lws2_32
 	X = .exe
 	gitexecdir = ../libexec/git-core

t/t4018-diff-funcname.sh

@@ -57,4 +57,10 @@ test_expect_success 'last regexp must not be negated' '
 	test_must_fail git diff --no-index Beer.java Beer-correct.java
 '
 
+test_expect_success 'alternation in pattern' '
+	git config diff.java.funcname "^[ 	]*\\(\\(public\\|static\\).*\\)$"
+	git diff --no-index Beer.java Beer-correct.java |
+	grep "^@@.*@@ public static void main("
+'
+
 test_done