fsmonitor-settings: stub in platform-specific incompatibility checking

Extend generic incompatibility checkout with platform-specific
mechanism.  Stub in Win32 version.

In the existing fsmonitor-settings code we have a way to mark
types of repos as incompatible with fsmonitor (whether via the
hook and ipc APIs).  For example, we do this for bare repos,
since there are no files to watch.

Extend this exclusion mechanism for platfor-specific reasons.
This commit just creates the framework and adds a stub for Win32.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>

Makefile

@@ -476,6 +476,11 @@ all::
 # `compat/fsmonitor/fsm-listen-<name>.c` that implements the
 # `fsm_listen__*()` routines.
 #
+# If your platform has os-specific ways to tell if a repo is incompatible with
+# fsmonitor (whether the hook or ipc daemon version), set FSMONITOR_OS_SETTINGS
+# to the "<name>" of the corresponding `compat/fsmonitor/fsm-settings-<name>.c`
+# that implements the `fsm_os_settings__*()` routines.
+#
 # Define DEVELOPER to enable more compiler warnings. Compiler version
 # and family are auto detected, but could be overridden by defining
 # COMPILER_FEATURES (see config.mak.dev). You can still set
@@ -1949,6 +1954,11 @@ ifdef FSMONITOR_DAEMON_BACKEND
 	COMPAT_OBJS += compat/fsmonitor/fsm-listen-$(FSMONITOR_DAEMON_BACKEND).o
 endif
 
+ifdef FSMONITOR_OS_SETTINGS
+	COMPAT_CFLAGS += -DHAVE_FSMONITOR_OS_SETTINGS
+	COMPAT_OBJS += compat/fsmonitor/fsm-settings-$(FSMONITOR_OS_SETTINGS).o
+endif
+
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK = NoThanks
 endif
@@ -2826,6 +2836,9 @@ GIT-BUILD-OPTIONS: FORCE
 ifdef FSMONITOR_DAEMON_BACKEND
 	@echo FSMONITOR_DAEMON_BACKEND=\''$(subst ','\'',$(subst ','\'',$(FSMONITOR_DAEMON_BACKEND)))'\' >>$@+
 endif
+ifdef FSMONITOR_OS_SETTINGS
+	@echo FSMONITOR_OS_SETTINGS=\''$(subst ','\'',$(subst ','\'',$(FSMONITOR_OS_SETTINGS)))'\' >>$@+
+endif
 ifdef TEST_OUTPUT_DIRECTORY
 	@echo TEST_OUTPUT_DIRECTORY=\''$(subst ','\'',$(subst ','\'',$(TEST_OUTPUT_DIRECTORY)))'\' >>$@+
 endif

compat/fsmonitor/fsm-settings-win32.c

@@ -0,0 +1,9 @@
+#include "cache.h"
+#include "config.h"
+#include "repository.h"
+#include "fsmonitor-settings.h"
+
+enum fsmonitor_reason fsm_os__incompatible(struct repository *r)
+{
+	return FSMONITOR_REASON_ZERO;
+}

config.mak.uname

@@ -423,6 +423,7 @@ ifeq ($(uname_S),Windows)
 	#
 	#   SNPRINTF_RETURNS_BOGUS = YesPlease
 	FSMONITOR_DAEMON_BACKEND = win32
+	FSMONITOR_OS_SETTINGS = win32
 	NO_SVN_TESTS = YesPlease
 	RUNTIME_PREFIX = YesPlease
 	HAVE_WPGMPTR = YesWeDo
@@ -607,6 +608,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_MKDTEMP = YesPlease
 	NO_SVN_TESTS = YesPlease
 	FSMONITOR_DAEMON_BACKEND = win32
+	FSMONITOR_OS_SETTINGS = win32
 	RUNTIME_PREFIX = YesPlease
 	HAVE_WPGMPTR = YesWeDo
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease

contrib/buildsystems/CMakeLists.txt

@@ -293,6 +293,11 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
 	list(APPEND compat_SOURCES compat/fsmonitor/fsm-listen-darwin.c)
 endif()
 
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+	add_compile_definitions(HAVE_FSMONITOR_OS_SETTINGS)
+	list(APPEND compat_SOURCES compat/fsmonitor/fsm-settings-win32.c)
+endif()
+
 set(EXE_EXTENSION ${CMAKE_EXECUTABLE_SUFFIX})
 
 #header checks

fsmonitor-settings.c

@@ -33,6 +33,18 @@ static int check_for_incompatible(struct repository *r)
 		return 1;
 	}
 
+#ifdef HAVE_FSMONITOR_OS_SETTINGS
+	{
+		enum fsmonitor_reason reason;
+
+		reason = fsm_os__incompatible(r);
+		if (reason != FSMONITOR_REASON_ZERO) {
+			set_incompatible(r, reason);
+			return 1;
+		}
+	}
+#endif
+
 	return 0;
 }
 

fsmonitor-settings.h

@@ -29,4 +29,17 @@ enum fsmonitor_reason fsm_settings__get_reason(struct repository *r,
 
 struct fsmonitor_settings;
 
+#ifdef HAVE_FSMONITOR_OS_SETTINGS
+/*
+ * Ask platform-specific code whether the repository is incompatible
+ * with fsmonitor (both hook and ipc modes).  For example, if the working
+ * directory is on a remote volume and mounted via a technology that does
+ * not support notification events.
+ *
+ * fsm_os__* routines should considered private to fsm_settings__
+ * routines.
+ */
+enum fsmonitor_reason fsm_os__incompatible(struct repository *r);
+#endif /* HAVE_FSMONITOR_OS_SETTINGS */
+
 #endif /* FSMONITOR_SETTINGS_H */