build: generate PublicInbox.pm with $VERSION

Thanks to git-describe, we can generate and update this
file to aid users in bug reporting.

1 files changed, 29 insertions, 0 deletions

diff --git a/version-gen.perl b/version-gen.perl
new file mode 100644
index 00000000..e9964e30
--- /dev/null
+++ b/version-gen.perl
@@ -0,0 +1,29 @@
+#!perl -w
+use v5.10.1;
+my $v = $ENV{VERSION} // die 'VERSION unset';
+my $f = './lib/PublicInbox.pm';
+if (-d ($ENV{GIT_DIR} // '.git') || -f '.git') {
+        chomp(my $gv = `git describe --match "v[0-9]*" HEAD`);
+        if ($? == 0) {
+                substr($gv, 0, 1, ''); # remove "v"
+                system(qw(git update-index -q --refresh));
+                if (my @n = `git diff-index --name-only HEAD --`) {
+                        $gv .= '-dirty';
+                }
+                $v = $gv;
+        }
+}
+$v =~ tr/-/./;
+if (-f $f && do $f && (eval('$PublicInbox::VERSION') // 'undef') eq $v) {
+        exit
+}
+my $tmp = "$f.tmp.$$";
+open my $fh, '>', $tmp  or die "open($tmp): $!";
+print $fh <<EOM or die "print($tmp): $!";
+# this file is generated by $0
+package PublicInbox;
+our \$VERSION = '$v';
+1;
+EOM
+close $fh or die "close($tmp): $!";
+rename($tmp, $f) or die "rename($tmp, $f): $!";