Concatenate content of TAGS files from different directories

Question

I'm referring to TAGS file generated by ctags or etags in order to have some code navigation in Emacs with M-..

The typical project looks like this:

• Large standard library (more than 100 files, but rarely updated).

• Project-specific library (updated on the daily basis).

I would like the project to be able to use two (or maybe more TAGS files), but regenerate only the portion of them, only the ones used inside the particular project. How would I approach this problem?

Answer 1

etags --help:

-i FILE, --include=FILE
     Include a note in tag file indicating that, when searching for
     a tag, one should also consult the tags file FILE after
     checking the current file.