use liblongpath if available

configure.ac

@@ -487,6 +487,14 @@ AC_DEFINE_UNQUOTED(ICONV_CONST, $am_cv_proto_iconv_arg1,
 
 dnl AC_MSG_NOTICE([Looking in libraries: $LIBS])
 
+# longpath support - see https://code.uplex.de/liblongpath/liblongpath
+# as long as rsync is single threaded, we can use _unsafe
+# NOTE: CHANGE THIS WHEN GOING MULTI-THREADED!
+AC_LIB_HAVE_LINKFLAGS([longpath_unsafe], [], [#include <longpath/longpath.h>])
+if test x$HAVE_LIBLONGPATH_UNSAFE = xyes; then
+   LIBS="$LIBS $LIBLONGPATH_UNSAFE"
+fi
+
 AC_CHECK_FUNCS(inet_ntop, , [AC_LIBOBJ(lib/inet_ntop)])
 AC_CHECK_FUNCS(inet_pton, , [AC_LIBOBJ(lib/inet_pton)])
 

flist.c

@@ -25,6 +25,9 @@
 #include "rounding.h"
 #include "inums.h"
 #include "io.h"
+#if defined HAVE_LIBLONGPATH_UNSAFE
+#include <longpath/longpath_redefine_defs.h>
+#endif
 
 extern int am_root;
 extern int am_server;

rsync.h

@@ -280,6 +280,10 @@ enum delret {
 
 #include "config.h"
 
+#if defined HAVE_LIBLONGPATH_UNSAFE
+#include <longpath/longpath_redefine_pre.h>
+#endif
+
 /* The default RSYNC_RSH is always set in config.h. */
 
 #include <stdio.h>
@@ -1289,3 +1293,7 @@ char *getpass(const char *prompt);
 #ifdef MAINTAINER_MODE
 const char *get_panic_action(void);
 #endif
+
+#if defined HAVE_LIBLONGPATH_UNSAFE
+#include <longpath/longpath_redefine_post.h>
+#endif

syscall.c

@@ -33,6 +33,10 @@
 #include <sys/syscall.h>
 #endif
 
+#if defined HAVE_LIBLONGPATH_UNSAFE
+#include <longpath/longpath_redefine_post.h>
+#endif
+
 extern int dry_run;
 extern int am_root;
 extern int am_sender;

xattrs.c

@@ -26,6 +26,10 @@
 
 #ifdef SUPPORT_XATTRS
 
+#if defined HAVE_LIBLONGPATH_UNSAFE
+#include <longpath/longpath_redefine_post.h>
+#endif
+
 extern int dry_run;
 extern int am_root;
 extern int am_sender;