I've also introduced a slightly new pattern for managing externals in subversion. New components get checked in as <name>-<version>.x, where <version> matches the exact vendor version string. After the initial import of the external component, the .x is tagged as .0 (i.e. tcl-8.4.18.x -> tcl-8.4.18.0). Some components may not need any tweaking, whereas there are others that might (tcl/tk fall into this bucket). In that case, the relevant modifications are made to the .x branch, which will be subsequently tagged as .1 (and then n+1 going forward) when they build successfully and all tests pass. Buildbots will be converted to rely on these explicit tags only, which makes it easy for us to switch them over to a new version as and when required. (Simple change to external(-amd64).bat: if we've bumped tcl to 8.4.18.1, change the .bat to rmdir 8.4.18.0 if it exists and check out a new .1 copy.)
