Ensure sane .version contents.

* top/GNUmakefile (_dummy): Also delete .version when rebuilding
version string.
* build-aux/git-version-gen: Improve documentation.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 44 insertions, 2 deletions

diff --git a/build-aux/git-version-gen b/build-aux/git-version-gen
index 5f819ba721..7aa025365d 100755
--- a/build-aux/git-version-gen
+++ b/build-aux/git-version-gen
@@ -1,8 +1,8 @@
 #!/bin/sh
 # Print a version string.
-scriptversion=2008-03-02.16
+scriptversion=2008-04-03.22
 
-# Copyright (C) 2007 Free Software Foundation
+# Copyright (C) 2007-2008 Free Software Foundation
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -26,6 +26,48 @@ scriptversion=2008-03-02.16
 # - from a non-git-repo directory containing a .tarball-version file, which
 #   presumes this script is invoked like "./git-version-gen .tarball-version".
 
+# In order to use intra-version strings in your project, you will need two
+# separate generated version string files:
+#
+# .tarball-version - present only in a distribution tarball, and not in
+#   a checked-out repository.  Created with contents that were learned at
+#   the last time autoconf was run, and used by git-version-gen.  Must not
+#   be present in either $(srcdir) or $(builddir) for git-version-gen to
+#   give accurate answers during normal development with a checked out tree,
+#   but must be present in a tarball when there is no version control system.
+#   Therefore, it cannot be used in any dependencies.  GNUmakefile has
+#   hooks to force a reconfigure at distribution time to get the value
+#   correct, without penalizing normal development with extra reconfigures.
+#
+# .version - present in a checked-out repository and in a distribution
+#   tarball.  Usable in dependencies, particularly for files that don't
+#   want to depend on config.h but do want to track version changes.
+#   Delete this file prior to any autoconf run where you want to rebuild
+#   files to pick up a version string change; and leave it stale to
+#   minimize rebuild time after unrelated changes to configure sources.
+#
+# It is probably wise to add these two files to .gitignore, so that you
+# don't accidentally commit either generated file.
+#
+# Use the following line in your configure.ac, so that $(VERSION) will
+# automatically be up-to-date each time configure is run (and note that
+# since configure.ac no longer includes a version string, Makefile rules
+# should not depend on configure.ac for version updates).
+#
+# AC_INIT([GNU project],
+#         m4_esyscmd([build-aux/git-version-gen .tarball-version]),
+#         [bug-project@example])
+#
+# Then use the following lines in your Makefile.am, so that .version
+# will be present for dependencies, and so that .tarball-version will
+# exist in distribution tarballs.
+#
+# BUILT_SOURCES = $(top_srcdir)/.version
+# $(top_srcdir)/.version:
+#	echo $(VERSION) > $@-t && mv $@-t $@
+# dist-hook:
+#	echo $(VERSION) > $(distdir)/.tarball-version
+
 case $# in
     1) ;;
     *) echo 1>&2 "Usage: $0 \$srcdir/.tarball-version"; exit 1;;