-## If we don't have a "version.i" or we have both files and they are different,
-## copy "version.i.tmp" over "version.i". This way the dependent targets are
-## only rebuilt when the version string changes.
+## Fetch the EXTRA_VERSION_NAME define from "version/extra_version_name" and output it
+## to "version.i.tmp".
+##
+## Fetch the EXTRA_VERSION_DESCRIPTION define from "version/extra_version_description",
+## sanitize and format it with a sed script to replace all non-alpha-numeric values
+## with "-" and join all lines by replacing "\n" with litteral string c-style "\n\t" and
+## output it to "version.i.tmp".
+##
+## If we don't have a "version.i" or we have both files (version.i, version.i.tmp)
+## and they are different, copy "version.i.tmp" over "version.i".
+## This way the dependent targets are only rebuilt when the git version
+## string or either one of extra version string change.