Add support for repo-local cgitrc file

When recursively scanning a directory tree looking for git repositories,
cgit will now parse cgitrc files found within such repositories.

The repo-specific config files can include any repo-specific options
except 'repo.url' and 'repo.path'. Also, in such config files the 'repo.'
prefix can not be used, i.e. the valid options then becomes:
* name
* clone-url
* desc
* ower
* defbranch
* snapshots
* enable-log-filecount
* enable-log-linecount
* max-stats
* module-link
* section
* about-filter
* commit-filter
* source-filter
* readme

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

cgitrc.5.txt

@@ -326,6 +326,15 @@ repo.url::
 	setting specified for each repo. Default value: none.
 
 
+REPOSITORY-SPECIFIC CGITRC FILE
+-------------------------------
+When the option 'scan-path' is used to auto-discover git repositories, cgit
+will try to parse the file 'cgitrc' within any found repository. Such a repo-
+specific config file may contain any of the repo-specific options described
+above, except 'repo.url' and 'repo.path'. Also, in a repo-specific config
+file, the 'repo.' prefix is dropped from the config option names.
+
+
 EXAMPLE CGITRC FILE
 -------------------