Batch renaming files with Bash

You could use bash's parameter expansion feature

for i in ./*.pkg ; do mv "$i" "${i/-[0-9.]*.pkg/.pkg}" ; done

Quotes are needed for filenames with spaces.

If all files are in the same directory the sequence

ls | 
sed -n 's/\(.*\)\(-[0-9.]*\.pkg\)/mv "\1\2" "\1.pkg"/p' | 
sh

will do your job. The sed command will create a sequence of mv commands, which you can then pipe into the shell. It's best to first run the pipeline without the trailing | sh so as to verify that the command does what you want.

To recurse through multiple directories use something like

find . -type f |
sed -n 's/\(.*\)\(-[0-9.]*\.pkg\)/mv "\1\2" "\1.pkg"/p' |
sh

Note that in sed the regular expression grouping sequence is brackets preceded by a backslash, \( and \), rather than single brackets ( and ).