tools/git-version-gen: use NEWS as a fallback

* define ".tarball-version" as the default if not specified by $1

* try read the version string from NEWS file as a fallback if the
  git-repository or .tarball-version is not available

Fixes: https://github.com/karelzak/util-linux/issues/1381
Signed-off-by: Karel Zak <kzak@redhat.com>

tools/git-version-gen

@@ -3,6 +3,7 @@
 scriptversion=2011-02-19.19; # UTC
 
 # Copyright (C) 2007-2011 Free Software Foundation, Inc.
+# Copyright (C) 2011-2021 Karel Zak <kzak@redhat.com>
 #
 # 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
@@ -22,10 +23,9 @@ scriptversion=2011-02-19.19; # UTC
 # - from a git repository in which the "git describe" command below
 #   produces useful output (thus requiring at least one signed tag)
 # - from a non-git-repo directory containing a .tarball-version file, which
-#   presumes this script is invoked like "./git-version-gen .tarball-version".
+#   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:
+# In order to use intra-version strings in your project, you will need:
 #
 # .tarball-version - present only in a distribution tarball, and not in
 #   a checked-out repository.  Created with contents that were learned at
@@ -44,6 +44,11 @@ scriptversion=2011-02-19.19; # UTC
 #   files to pick up a version string change; and leave it stale to
 #   minimize rebuild time after unrelated changes to configure sources.
 #
+# NEWS - present everywhere. It's used only as a fallback solution for
+#   3rd-party tarballs generated by the unofficial way (e.g. GitHub).
+#   The version string is read from the first line of the file, the expected
+#   format is "project-name version: date".
+#
 # It is probably wise to add these two files to .gitignore, so that you
 # don't accidentally commit either generated file.
 #
@@ -67,13 +72,13 @@ scriptversion=2011-02-19.19; # UTC
 #	echo $(VERSION) > $(distdir)/.tarball-version
 
 case $# in
-    1|2) ;;
-    *) echo 1>&2 "Usage: $0 \$srcdir/.tarball-version" \
-         '[TAG-NORMALIZATION-SED-SCRIPT]'
+    0|1|2) ;;
+    *) echo 1>&2 "Usage: $0 [[\$srcdir/.tarball-version]" \
+         '[TAG-NORMALIZATION-SED-SCRIPT]]'
        exit 1;;
 esac
 
-tarball_version_file=$1
+tarball_version_file=${1:-".tarball-version"}
 tag_sed_script="${2:-s/x/x/}"
 nl='
 '
@@ -125,7 +130,12 @@ then
     esac
     v_from_git=1
 else
-    v=UNKNOWN
+    if test -f NEWS
+    then
+	    v=`sed  '1s/.*[[:blank:]]\(.*\):.*/\1/; q;' NEWS`
+    else
+	    v=UNKNOWN
+    fi
 fi
 
 v=`echo "$v" |sed 's/^v//'`