Add Rugged::Config#get_all

This method allows you to fetch all values for a particular config,
similar to `git config --get-all "remote.origin.fetch"`.

For example, I have a git config with two `fetch` settings in one
remote:

```
$ cat ~/git/uart/.git/config
[core]
	repositoryformatversion = 0
	filemode = true
	bare = false
	logallrefupdates = true
	ignorecase = true
	precomposeunicode = true
[remote "origin"]
	url = [email protected]:tenderlove/uart.git
	fetch = +refs/heads/*:refs/remotes/origin/*
	fetch = +refs/heads/*:refs/remotes/lololol/*
[branch "master"]
	remote = origin
	merge = refs/heads/master
```

With `Rugged::Config#get_all` I can get the list of `fetch` options from
the config:

```
$ ruby -I lib -rrugged -e'p Rugged::Repository.new("/Users/aaron/git/uart").config.get_all("remote.origin.fetch")'
["+refs/heads/*:refs/remotes/origin/*", "+refs/heads/*:refs/remotes/lololol/*"]
```

References #725

Author: tenderlove

ext/rugged/rugged_config.c

@@ -354,6 +354,44 @@ static VALUE rb_git_config_transaction(VALUE self)
 	return rb_result;
 }
 
+static int each_config_value(const git_config_entry * entry, void *ctx)
+{
+	VALUE list = (VALUE)ctx;
+	rb_ary_push(list, rb_str_new_utf8(entry->value));
+	return 0;
+}
+
+/*
+ *  call-seq:
+ *    cfg.get_all(key) -> [value1, value2, ...]
+ *
+ *  Get a list of values for the given config +key+. Values are always
+ *  returned as an +Array+ of +String+, or +nil+ if the given key doesn't exist
+ *  in the Config file.
+ *
+ *    cfg['apply.whitespace'] #=> ['fix']
+ *    cfg['diff.renames'] #=> ['true']
+ *    cfg['remote.origin.fetch'] #=> ["+refs/heads/*:refs/remotes/origin/*", "+refs/heads/*:refs/lolol/origin/*"]
+ */
+static VALUE rb_git_config_get_all(VALUE self, VALUE key)
+{
+	git_config *config;
+	VALUE list;
+	int error;
+
+	Data_Get_Struct(self, git_config, config);
+
+	list = rb_ary_new();
+	error = git_config_get_multivar_foreach(
+		config, StringValueCStr(key), NULL, each_config_value, (void *)list);
+
+	if (error == GIT_ENOTFOUND)
+		return Qnil;
+
+	rugged_exception_check(error);
+	return list;
+}
+
 void Init_rugged_config(void)
 {
 	/*
@@ -372,6 +410,7 @@ void Init_rugged_config(void)
 
 	rb_define_method(rb_cRuggedConfig, "get", rb_git_config_get, 1);
 	rb_define_method(rb_cRuggedConfig, "[]", rb_git_config_get, 1);
+	rb_define_method(rb_cRuggedConfig, "get_all", rb_git_config_get_all, 1);
 
 	rb_define_method(rb_cRuggedConfig, "each_key", rb_git_config_each_key, 0);
 	rb_define_method(rb_cRuggedConfig, "each_pair", rb_git_config_each_pair, 0);

test/config_test.rb

@@ -5,6 +5,13 @@ def setup
     @repo = FixtureRepo.from_rugged("testrepo.git")
   end
 
+  def test_multi_fetch
+    config = @repo.config
+    fetches = ["+refs/heads/*:refs/remotes/test_remote/*",
+               "+refs/heads/*:refs/remotes/hello_remote/*"]
+    assert_equal fetches, config.get_all("remote.test_multiple_fetches.fetch")
+  end
+
   def test_read_config_file
     config = @repo.config
     assert_equal 'false', config['core.bare']

test/fixtures/testrepo.git/config

@@ -11,3 +11,6 @@
 	pushurl = git://github.com/libgit2/TestEmptyRepository.git
 	fetch = +refs/heads/*:refs/remotes/test_remote/*
 	push = refs/heads/*:refs/heads/testing/*
+[remote "test_multiple_fetches"]
+	fetch = +refs/heads/*:refs/remotes/test_remote/*
+	fetch = +refs/heads/*:refs/remotes/hello_remote/*