28.1.12.4 Inserting Version Control Headers

On Subversion, CVS, RCS, and SCCS, you can put certain special strings called version headers into a work file. When the file is committed, the version control system automatically puts the revision number, the name of the user who made the commit, and other relevant information into the version header.

VC does not normally use the information in the version headers. As an exception, when using RCS, Emacs uses the version header, if there is one, to determine the file version, since it is often more reliable than the RCS master file. To inhibit using the version header this way, change the variable vc-consult-headers to nil. VC then always uses the file permissions (if it is supposed to trust them), or else checks the master file.

To insert a suitable header string into the current buffer, use the command M-x vc-insert-headers. This command works only on Subversion, CVS, RCS, and SCCS. The variable vc-backend-header contains the list of keywords to insert into the version header; for instance, CVS uses vc-cvs-header, whose default value is '("\$Id\$"). (The extra backslashes prevent the string constant from being interpreted as a header, if the Emacs Lisp file defining it is maintained with version control.) The vc-insert-headers command inserts each keyword in the list on a new line at point, surrounded by tabs, and inside comment delimiters if necessary.

The variable vc-static-header-alist specifies further strings to add based on the name of the buffer. Its value should be a list of elements of the form (regexp . format). Whenever regexp matches the buffer name, format is also inserted as part of the version header. A ‘ %s’ in format is replaced with the file’s version control type.