Add FORCE_FUSE build option and fix hardcoded version

- Remove hardcoded FUSE_USE_VERSION defines from source files
- Add FORCE_FUSE=2 or FORCE_FUSE=3 Makefile option to override detection
- Fix FUSE 2 channel tracking (psync_fuse_channel variable)
- Properly store and use channel in mount/unmount for FUSE 2

Usage:
  make                  # Auto-detect (prefers FUSE 3)
  make FORCE_FUSE=2     # Force FUSE 2 build
  make FORCE_FUSE=3     # Force FUSE 3 build

Verified both FUSE 2 and FUSE 3 builds work correctly.

Makefile

@@ -5,8 +5,19 @@ AR		:= ar
 DIST_CFLAGS	:= $(CFLAGS)
 DIST_CXXFLAGS	:= $(CXXFLAGS)
 
-# Detect FUSE version
-FUSE_VERSION	:= $(shell ./detect_fuse.sh)
+# Detect FUSE version (can be overridden with FORCE_FUSE=2 or FORCE_FUSE=3)
+ifdef FORCE_FUSE
+    ifeq ($(FORCE_FUSE),2)
+        FUSE_VERSION := FUSE2
+    else ifeq ($(FORCE_FUSE),3)
+        FUSE_VERSION := FUSE3
+    else
+        $(error FORCE_FUSE must be 2 or 3)
+    endif
+else
+    FUSE_VERSION := $(shell ./detect_fuse.sh)
+endif
+
 ifeq ($(FUSE_VERSION),FUSE3)
     FUSE_CFLAGS := $(shell pkg-config --cflags fuse3)
     FUSE_LIBS := -lfuse3

pclsync/pfs.c

@@ -28,8 +28,6 @@
   DAMAGE.
 */
 
-#define FUSE_USE_VERSION 30
-
 #include <errno.h>
 #include <fuse.h>
 #include <pthread.h>
@@ -94,6 +92,9 @@ typedef off_t fuse_off_t;
 
 static int shutdown_in_progress = 0;
 static struct fuse *psync_fuse = NULL;
+#if FUSE_USE_VERSION < 30
+static struct fuse_chan *psync_fuse_channel = NULL;
+#endif
 static char *psync_current_mountpoint = NULL;
 static psync_generic_callback_t psync_start_callback = NULL;
 char *pfs_fake_prefix = NULL;
@@ -3600,7 +3601,8 @@ static void pfs_do_stop(void) {
         struct fuse_session *se = fuse_get_session(psync_fuse);
         fuse_session_unmount(se);
 #else
-        fuse_unmount(mp, fuse_get_session(psync_fuse));
+        fuse_unmount(mp, psync_fuse_channel);
+        psync_fuse_channel = NULL;
 #endif
         clock_gettime(CLOCK_REALTIME, &ts);
 
@@ -3862,6 +3864,7 @@ static int pfs_do_start() {
     fuse_unmount(mp, ch);
     goto err0;
   }
+  psync_fuse_channel = ch;
 #endif
   
   psync_current_mountpoint = mp;

pclsync/pfsxattr.c

@@ -29,8 +29,6 @@
    DAMAGE.
 */
 
-#define FUSE_USE_VERSION 30
-
 #include <errno.h>
 #include <fuse.h>
 #include <string.h>