Fix 'Bootstrap' to bypass a problem with "bk changes" by changing the...

Fix 'Bootstrap' to bypass a problem with "bk changes" by changing the directory before calling the command.


Build-tools/Bootstrap:
  Bypass a BK problem with "bk changes": It stopped delivering changeset comments when
  1) it encountered a single, unbroken line with about 1k characters  AND
  2) it was applied not to the current directory but to a named BK root directory.
  
  As 1) cannot be changed post-factum (and might happen again),
  the "bk changes" command is now preceded by a "cd $REPO".
  
  Do some renaming of variables used around the "bk changes" call to improve documentation.

Build-tools/Bootstrap

@@ -240,35 +240,47 @@ if (defined $opt_changelog)
 	# the last tagged ChangeSet (this relies heavily on our current tagging
 	# practice!)
 	#
-	my $revision= "";
+	$opt_changelog=~ s/^=//;	# Sometimes, a leading '=' was not stripped.
+	my $log_base= $opt_changelog;
+	my $changelogfile;
+	if ($target_dir =~ m:^/:)	# we need an absolute path, as we change directory
+	{
+		$changelogfile= $target_dir. "/ChangeLog";
+	}
+	else
+	{
+		$changelogfile= cwd() . "/" . $target_dir . "/ChangeLog";
+	}
+
 	if ($opt_changelog eq "last")
 	{
 		if (!$opt_revision)
 		{
-			$revision= `bk changes -t -d':REV:::TAG:' -n $REPO | grep mysql-$major.$minor | head -1 | cut -f1 -d ":"`;
+			$log_base= `bk changes -t -d':REV:::TAG:' -n $REPO | grep mysql-$major.$minor | head -1 | cut -f1 -d ":"`;
 		}
 		else
 		{
-			$revision= `bk changes -r..$opt_revision -t -d':REV:' -n $REPO | head -2 | tail -1`;
+			$log_base= `bk changes -r..$opt_revision -t -d':REV:' -n $REPO | head -2 | tail -1`;
 		}
-		chomp($revision);
-		$opt_changelog= $revision;
+		chomp($log_base);
 	}
 
-	$msg= "Adding $target_dir/ChangeLog";
-	$msg.= " (down to revision $opt_changelog)" if $opt_changelog ne "";
+	$msg= "Adding $changelogfile";
+	$msg.= " (down to revision $log_base)" if $log_base ne "";
 	&logger($msg);
-	$command= "bk changes -v";
-	$command.= " -r" if ($opt_changelog ne "" || $opt_revision);
-	$command.= $opt_changelog if $opt_changelog ne "";
-	$command.= ".." if ($opt_changelog ne "" && !$opt_revision);
+	# Due to a BK error, "bk changes" must be run in $REPO !
+	$command= "cd $REPO ; ";
+	$command.= "bk changes -v";
+	$command.= " -r" if ($log_base ne "" || $opt_revision);
+	$command.= $log_base if $log_base ne "";
+	$command.= ".." if ($log_base ne "" && !$opt_revision);
 	$command.= ".." . $opt_revision if $opt_revision;
-	$command.= " " . $REPO . " > $target_dir/ChangeLog";
+	$command.= " > $changelogfile";
 	&logger($command);
 	# We cannot use run_command here because of output redirection
 	unless ($opt_dry_run)
 	{
-		system($command) == 0 or &abort("Could not create $target_dir/ChangeLog!");
+		system($command) == 0 or &abort("Could not create $changelogfile!");
 	}
 }