formats/config: Added encoder/decoder for git config files. (#97)

* WIP: Add config format parser.

* add decoder based on gcfg.

Portions of code taken from:
https://github.com/go-gcfg/gcfg/blob/5b9f94ee80b2331c3982477bd84be8edd857df33/read.go

* add git config encoder and config methods.

* use format/config in storage/filesystem for read

* use format/config in storage/filesystem to write

* formats/config: improve docs.

* formats/config: improve tests.

* formats/config: use our fork of gcfg; improve api.

* formats/config: improve api.

* storage/filesystem: fix gofmt

* formats/config: use NoSubsection constant.

* formats/config: add doc.go

* formats/config: requested sytle changes.

* formats/config: do not use *_test packages.

1 files changed, 83 insertions, 0 deletions

diff --git a/formats/config/option.go b/formats/config/option.go
new file mode 100644
index 0000000..dbb401c
--- /dev/null
+++ b/formats/config/option.go
@@ -0,0 +1,83 @@
+package config
+
+import (
+	"strings"
+)
+
+type Option struct {
+	// Key preserving original caseness.
+	// Use IsKey instead to compare key regardless of caseness.
+	Key string
+	// Original value as string, could be not notmalized.
+	Value string
+}
+
+type Options []*Option
+
+// IsKey returns true if the given key matches
+// this options' key in a case-insensitive comparison.
+func (o *Option) IsKey(key string) bool {
+	return strings.ToLower(o.Key) == strings.ToLower(key)
+}
+
+// Get gets the value for the given key if set,
+// otherwise it returns the empty string.
+//
+// Note that there is no difference
+//
+// This matches git behaviour since git v1.8.1-rc1,
+// if there are multiple definitions of a key, the
+// last one wins.
+//
+// See: http://article.gmane.org/gmane.linux.kernel/1407184
+//
+// In order to get all possible values for the same key,
+// use GetAll.
+func (opts Options) Get(key string) string {
+	for i := len(opts) - 1; i >= 0; i-- {
+		o := opts[i]
+		if o.IsKey(key) {
+			return o.Value
+		}
+	}
+	return ""
+}
+
+// GetAll returns all possible values for the same key.
+func (opts Options) GetAll(key string) []string {
+	result := []string{}
+	for _, o := range opts {
+		if o.IsKey(key) {
+			result = append(result, o.Value)
+		}
+	}
+	return result
+}
+
+func (opts Options) withoutOption(key string) Options {
+	result := Options{}
+	for _, o := range opts {
+		if !o.IsKey(key) {
+			result = append(result, o)
+		}
+	}
+	return result
+}
+
+func (opts Options) withAddedOption(key string, value string) Options {
+	return append(opts, &Option{key, value})
+}
+
+func (opts Options) withSettedOption(key string, value string) Options {
+	for i := len(opts) - 1; i >= 0; i-- {
+		o := opts[i]
+		if o.IsKey(key) {
+			result := make(Options, len(opts))
+			copy(result, opts)
+			result[i] = &Option{key, value}
+			return result
+		}
+	}
+
+	return opts.withAddedOption(key, value)
+}