configure.ac: Better handling of --enable-git-version

Multiple messages were put on the same line, so the output could be a
bit confusing. Also, it didn't fail on error, i.e. if git or .git were
missing the configure still ran successfully, but git version wasn't
enabled.

Now all messages are on their own line, if git or .git is not found,
an error occurs, and on success the version ("kalu version x.y.z") is
suffixed with "-git"

configure.ac

@@ -117,29 +117,33 @@ AC_DEFINE_UNQUOTED([AUR_URL_PREFIX_PKG], ["$AUR_URL_PREFIX_PKG"],
 	[Prefix before each package to construct AUR URL])
 
 # git version
-AC_MSG_CHECKING([whether to use git version if available])
+AC_MSG_CHECKING([if git version must be used])
 if test "x$wantgitver" = "xyes"; then
+    AC_MSG_RESULT([yes])
     AC_CHECK_PROGS([GIT], [git])
+    if test "x$GIT" = "x"; then
+        AC_MSG_ERROR([Cannot use git version: git not found])
+    fi
     AC_CHECK_FILE([.git/], hasgitdir=yes)
-    if test $GIT -a "x$hasgitdir" = "xyes"; then
-        AC_MSG_RESULT([yes])
+    if test "x$hasgitdir" = "xyes"; then
         usegitver=yes
+        gitver=-git
         AC_DEFINE([USE_GIT_VERSION], , [Use GIT version])
     else
-        AC_MSG_RESULT([no, git or .git dir missing])
-        usegitver=no
+        AC_MSG_ERROR([Cannot use git version: .git not found])
     fi
 else
-    AC_MSG_RESULT([no, disabled])
+    AC_MSG_RESULT([no])
     usegitver=no
+    gitver=
 fi
 AM_CONDITIONAL(USE_GIT_VERSION, test "x$usegitver" = "xyes")
 
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT
 
 echo "
-	${PACKAGE} version ${PACKAGE_VERSION}
+	${PACKAGE} version ${PACKAGE_VERSION}${gitver}
 
  Build information:
    source code location		: ${srcdir}