Designing: updating tags file incrementally

Situation

project
project/a.c
project/b.c
project/i.h
project/tags

Sub issues

Where do timestamps (and content hash values) of input files go?

1. introducing a pseudo tag like !_SOURCE_FILE_TIMESTAMP!/project/path/something.c or
2. introducing timestamp: fields for F/file kind tags
3. introducing special "filesystem" language and handling such information in the language

Which items in the command line used in generating the tags file should be recorded?

• enabled kinds (done)
• enabled common fields
• enabled parser specific fields
• enabled extras
• enabled parser specific fields
• parser specific parameters (?)
• enabled pseudo tags (?)