Require templated header / footer on matching files

Description

Method to allow easy insertion of header/footer text in files with names matching defined patterns and to check for and enforce its existence.

This will allow customers to easily handle a variety of situations that require specific information to appear at the top and/or bottom of certain types of files. These situations include (but are not limited to) the the following:

• Security classification
• Copyright information
• License information

These settings should be configurable overall for the server, for individual groups, or for individual projects.

Proposal

Web GUI:

• Drop-down links for header/footer templates (similar to .gitignore, etc.)
• Administrative configuration of the following on a per server / group / project basis:
  • Templates for headers/footers
  • Templates for matching file selection
  • Rejection message
  • Commit pass/fail REGEXP

Commit / push hook:

Implement a hook that fires on admin-selected files and that uses a REGEXP to check for required text at the top/bottom of each matching file at commit / push time. Non-conforming commits will be rejected with an appropriate error message

Links / references

http://www.cdse.edu/documents/cdse/Marking_Classified_Information.pdf

Documentation blurb

TBD - similar to the way other templates work

/cc: @pauldalmeida @victorwu