build: change version number generation

Force Makefile to always run version.sh to potentially regenerate
version.h. Drop compiler version and 'git-' prefix from version
number. Match only git tags starting 'v'+number when generating
version number; leave the 'v' out from the result.

Makefile

@@ -632,8 +632,11 @@ config.mak: configure
 	@echo "####### Please run ./configure again - it's changed! #######"
 	@echo "############################################################"
 
-version.h: version.sh
-	./$< `$(CC) -dumpversion`
+version.h .version: version.sh
+	./$<
+
+# Force version.sh to run to potentially regenerate version.h
+-include .version
 
 %$(EXESUF): %.c
 	$(CC) $(CFLAGS) -o $@ $^
@@ -855,7 +858,7 @@ driversclean:
 -include $(DEP_FILES)
 
 .PHONY: all doxygen locales *install* *tools drivers
-.PHONY: checkheaders *clean tests
+.PHONY: checkheaders *clean tests .version
 
 # Disable suffix rules.  Most of the builtin rules are suffix rules,
 # so this saves some time on slow systems.

configure

@@ -7286,8 +7286,6 @@ cmp -s "$TMPH" config.h || mv -f "$TMPH" config.h
 
 #############################################################################
 
-./version.sh `$_cc -dumpversion`
-
 cat << EOF
 
 Config files successfully generated by ./configure $configuration !

version.sh

@@ -5,8 +5,8 @@ test "$1" && extra="-$1"
 # Extract revision number from file used by daily tarball snapshots
 # or from "git describe" output
 git_revision=$(cat snapshot_version 2> /dev/null)
-test $git_revision || test ! -d .git || git_revision=`git describe --always`
-test $git_revision && git_revision=git-$git_revision
+test $git_revision || test ! -d .git || git_revision=`git describe --match "v[0-9]*" --always`
+git_revision=$(expr "$git_revision" : v*'\(.*\)')
 test $git_revision || git_revision=UNKNOWN
 
 # releases extract the version number from the VERSION file