Use git description as the tinc version.

Instead of using the hardcoded version number in configure.ac, this
makes tinc use the live version reported by "git describe",
queried on-the-fly during the build process and regenerated for every
build.

This makes tinc version output more useful, as tinc will now display the
number of commits since the last tag as well as the commit the binary is
built from, following the format described in git-describe(1).

Here's an example of tincd --version output:

  tinc version release-1.1pre10-48-gc149315 (built Jun 29 2014 15:21:10, protocol 17.3)

When building directly from a release tag, this will look like the following:

  tinc version release-1.1pre10 (built Jun 29 2014 15:21:10, protocol 17.3)

(Note that the format is slightly different - because of the way the
tags are named, it says "release-1.1pre10" instead of just "1.1pre10")

If git describe fails (for example when building from a release
tarball), the build automatically falls back to the autoconf-provided
VERSION macro (i.e. the old behavior).

src/Makefile.am

@@ -2,9 +2,12 @@
 
 sbin_PROGRAMS = tincd tinc sptps_test sptps_keypair
 
-## Make sure version.c is always rebuilt
-.PHONY: version.c
-version.c:
+## Make sure version.c is always rebuilt with the latest git information
+.PHONY: version.c version_git.h
+version_git.h:
+	echo >$@
+	-GIT_DESCRIPTION="`cd $(@D) && git describe`" && echo "#define GIT_DESCRIPTION \"$$GIT_DESCRIPTION\"" >$@
+version.c: version_git.h
 
 if LINUX
 sbin_PROGRAMS += sptps_speed
@@ -91,7 +94,7 @@ tincd_SOURCES = \
 	tincd.c \
 	utils.c utils.h \
 	xalloc.h \
-	version.c version.h \
+	version.c version.h version_git.h \
 	ed25519/ecdh.c \
 	ed25519/ecdsa.c \
 	$(ed25519_SOURCES) \
@@ -113,7 +116,7 @@ tinc_SOURCES = \
 	tincctl.c tincctl.h \
 	top.c top.h \
 	utils.c utils.h \
-	version.c version.h \
+	version.c version.h version_git.h \
 	ed25519/ecdh.c \
 	ed25519/ecdsa.c \
 	ed25519/ecdsagen.c \

src/process.c

@@ -223,7 +223,7 @@ bool detach(void) {
 	openlogger(identname, logmode);
 
 	logger(DEBUG_ALWAYS, LOG_NOTICE, "tincd %s (%s %s) starting, debug level %d",
-			   VERSION, BUILD_DATE, BUILD_TIME, debug_level);
+			   BUILD_VERSION, BUILD_DATE, BUILD_TIME, debug_level);
 
 	return true;
 }

src/tincctl.c

@@ -88,7 +88,7 @@ static struct option const long_options[] = {
 
 static void version(void) {
 	printf("%s version %s (built %s %s, protocol %d.%d)\n", PACKAGE,
-		   VERSION, BUILD_DATE, BUILD_TIME, PROT_MAJOR, PROT_MINOR);
+		   BUILD_VERSION, BUILD_DATE, BUILD_TIME, PROT_MAJOR, PROT_MINOR);
 	printf("Copyright (C) 1998-2014 Ivo Timmermans, Guus Sliepen and others.\n"
 			"See the AUTHORS file for a complete list.\n\n"
 			"tinc comes with ABSOLUTELY NO WARRANTY.  This is free software,\n"

src/tincd.c

@@ -343,7 +343,7 @@ int main(int argc, char **argv) {
 
 	if(show_version) {
 		printf("%s version %s (built %s %s, protocol %d.%d)\n", PACKAGE,
-			   VERSION, BUILD_DATE, BUILD_TIME, PROT_MAJOR, PROT_MINOR);
+			   BUILD_VERSION, BUILD_DATE, BUILD_TIME, PROT_MAJOR, PROT_MINOR);
 		printf("Copyright (C) 1998-2014 Ivo Timmermans, Guus Sliepen and others.\n"
 				"See the AUTHORS file for a complete list.\n\n"
 				"tinc comes with ABSOLUTELY NO WARRANTY.  This is free software,\n"

src/version.c

@@ -18,7 +18,14 @@
 */
 
 #include "version.h"
+#include "version_git.h"
+#include "../config.h"
 
 /* This file is always rebuilt (even if there are no changes) so that the following is updated */
 const char* const BUILD_DATE = __DATE__;
 const char* const BUILD_TIME = __TIME__;
+#ifdef GIT_DESCRIPTION
+const char* const BUILD_VERSION = GIT_DESCRIPTION;
+#else
+const char* const BUILD_VERSION = VERSION;
+#endif

src/version.h

@@ -22,5 +22,6 @@
 
 extern const char* const BUILD_DATE;
 extern const char* const BUILD_TIME;
+extern const char* const BUILD_VERSION;
 
 #endif /* __TINC_VERSION_H__ */