Introduce functionality for automatically fetching package versions

Created by: htho-lgs

Versions of the packages included in update file needs to be entered manually in sw-description file or provided in as a bitbake variable.

This patch searches for a group[1] in sw-description file containing the tag "SWU_AUTO_VERSION". If found, the version of the corresponding package is fetched from it's package-data-file (PV) and the tag is replaced with the version. Possible trailing strings in PV starting with + (e.g. "+gitAUTOINC+...") are dropped to keep semantic versions.

Since the filenames not always belong to the package name (deployed with another name or the file is a container for the real package) support providing the correct package name by appending the tag with :<package-name>.

[1] http://www.hyperrealm.com/libconfig/libconfig_manual.html#Groups

Signed-off-by: Thomas Haemmerle thomas.haemmerle@leica-geosystems.com