git-svn: Add per-svn-remote ignore-paths config

The --ignore-paths option to fetch is very useful for working on a subset
of a SVN repository.  For proper operation, every command that causes a
fetch (explicit or implied) must include a matching --ignore-paths option.

This patch adds a persistent svn-remote.$repo_id.ignore-paths config by
promoting Fetcher::is_path_ignored to a member function and initializing
$self->{ignore_regex} in Fetcher::new.  Command line --ignore-paths is
still recognized and acts in addition to the config value.

Signed-off-by: Ben Jackson <ben@ben.com>
Acked-by: Eric Wong <normalperson@yhbt.net>

Documentation/git-svn.txt

@@ -107,17 +107,25 @@ repository, either don't use this option or you should both use it in
 the same local timezone.
 
 --ignore-paths=<regex>;;
-	This allows one to specify Perl regular expression that will
+	This allows one to specify a Perl regular expression that will
 	cause skipping of all matching paths from checkout from SVN.
-	Examples:
+	The '--ignore-paths' option should match for every 'fetch'
+	(including automatic fetches due to 'clone', 'dcommit',
+	'rebase', etc) on a given repository.
 
-	--ignore-paths="^doc" - skip "doc*" directory for every fetch.
+config key: svn-remote.<name>.ignore-paths
 
-	--ignore-paths="^[^/]+/(?:branches|tags)" - skip "branches"
-	    and "tags" of first level directories.
+	If the ignore-paths config key is set and the command
+	line option is also given, both regular expressions
+	will be used.
 
-	Regular expression is not persistent, you should specify
-	it every time when fetching.
+Examples:
+
+	--ignore-paths="^doc" - skip "doc*" directory for every
+	    fetch.
+
+	--ignore-paths="^[^/]+/(?:branches|tags)" - skip
+	    "branches" and "tags" of first level directories.
 
 'clone'::
 	Runs 'init' and 'fetch'.  It will automatically create a