Added 'version' command to print when the bcachefs tool was built

Makefile

@@ -13,9 +13,12 @@ CFLAGS+=-std=gnu89 -O2 -g -MMD -Wall				\
 	-DNO_BCACHEFS_CHARDEV					\
 	-DNO_BCACHEFS_FS					\
 	-DNO_BCACHEFS_SYSFS					\
+	-DVERSION_STRING='"$(VERSION)"'				\
 	$(EXTRA_CFLAGS)
 LDFLAGS+=$(CFLAGS)
 
+VERSION?=$(shell git describe --long --dirty 2>/dev/null || echo 0.1-nogit)
+
 CC_VERSION=$(shell $(CC) -v 2>&1|grep -E '(gcc|clang) version')
 
 ifneq (,$(findstring gcc,$(CC_VERSION)))
@@ -56,6 +59,16 @@ DEPS=$(SRCS:.c=.d)
 OBJS=$(SRCS:.c=.o)
 bcachefs: $(OBJS)
 
+# If the version string differs from the last build, update the last version
+ifneq ($(VERSION),$(shell cat .version 2>/dev/null))
+.PHONY: .version
+endif
+.version:
+	echo '$(VERSION)' > $@
+
+# Rebuild the 'version' command any time the version string changes
+cmd_version.o : .version
+
 .PHONY: install
 install: bcachefs
 	mkdir -p $(DESTDIR)$(ROOT_SBINDIR)

bcachefs.8

@@ -1,5 +1,5 @@
-.Dd February 9, 2018
+.Dd May 26, 2018
-.Dt BCACHEFS 8
+.Dt BCACHEFS 8 SMM
 .Os
 .Sh NAME
 .Nm bcachefs
@@ -87,6 +87,11 @@ Dump filesystem metadata to a qcow2 image
 .It Ic list
 List filesystem metadata in textual form
 .El
+.Ss Miscellaneous commands
+.Bl -tag -width 18n -compact
+.It Ic version
+Display the version of the invoked bcachefs tool
+.El
 .Sh Superblock commands
 .Bl -tag -width Ds
 .It Nm Ic format Oo Ar options Oc Ar devices\ ...
@@ -310,5 +315,10 @@ Verbose mode
 List mode
 .El
 .El
+.Sh Miscellaneous commands
+.Bl -tag -width Ds
+.It Nm Ic version
+Display the version of the invoked bcachefs tool
+.El
 .Sh EXIT STATUS
 .Ex -std

bcachefs.c

@@ -70,7 +70,10 @@ static void usage(void)
 	     "Debug:\n"
 	     "These commands work on offline, unmounted filesystems\n"
 	     "  dump                 Dump filesystem metadata to a qcow2 image\n"
-	     "  list                 List filesystem metadata in textual form\n");
+	     "  list                 List filesystem metadata in textual form\n"
+	     "\n"
+	     "Miscellaneous:\n"
+	     "  version              Display the version of the invoked bcachefs tool\n");
 }
 
 static char *full_cmd;
@@ -144,6 +147,8 @@ int main(int argc, char *argv[])
 
 	char *cmd = pop_cmd(&argc, argv);
 
+	if (!strcmp(cmd, "version"))
+		return cmd_version(argc, argv);
 	if (!strcmp(cmd, "format"))
 		return cmd_format(argc, argv);
 	if (!strcmp(cmd, "show-super"))

cmd_version.c

@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+#include "cmds.h"
+
+int cmd_version(int argc, char *argv[])
+{
+	printf("bcachefs tool version %s\n", VERSION_STRING);
+	return 0;
+}

cmds.h

@@ -43,4 +43,6 @@ int cmd_list(int argc, char *argv[]);
 int cmd_migrate(int argc, char *argv[]);
 int cmd_migrate_superblock(int argc, char *argv[]);
 
+int cmd_version(int argc, char *argv[]);
+
 #endif /* _CMDS_H */