Introduce 'section' as canonical spelling for 'repo.group'

The 'repo.' prefix should be reserved for repo-specific options, but
the option 'repo.group' must still be honored to stay backwards
compatible.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgitrc.5.txt

@@ -200,8 +200,8 @@ renamelimit::
 	  `man git-diff`). Default value: "-1".
 
 repo.group::
-	A value for the current repository group, which all repositories
-	specified after this setting will inherit. Default value: none.
+	Legacy alias for 'section' which will be deprecated starting with
+	cgit-1.0.
 
 robots::
 	Text used as content for the "robots" meta-tag. Default value:
@@ -225,6 +225,11 @@ scan-path::
 	the result will be cached as a cgitrc include-file in the cache
 	directory. Default value: none. See also: cache-scanrc-ttl.
 
+section:
+	The name of the current repository section - all repositories defined
+	after this option will inherit the current section name. Default value:
+	none.
+
 snapshots::
 	Text which specifies the default set of snapshot formats generated by
 	cgit. The value is a space-separated list of zero or more of the