[GITEA] Improved Linguist compatibility

Recognise the `linguist-documentation` and `linguist-detectable`
attributes in `.gitattributes` files, and use them in
`GetLanguageStats()` to make a decision whether to include a particular
file in the stats or not.

This allows one more control over which files in their repositories
contribute toward the language statistics, so that for a project that is
mostly documentation, the language stats can reflect that.

Fixes #1672.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
(cherry picked from commit 6d4e02fe5f)
(cherry picked from commit ee1ead8189)
(cherry picked from commit 2dbec730e8)

modules/git/repo_language_stats.go

@@ -13,6 +13,18 @@ const (
 	bigFileSize   int64 = 1024 * 1024 // 1 MiB
 )
 
+type LinguistBoolAttrib struct {
+	Value string
+}
+
+func (attrib *LinguistBoolAttrib) IsTrue() bool {
+	return attrib.Value == "set" || attrib.Value == "true"
+}
+
+func (attrib *LinguistBoolAttrib) IsFalse() bool {
+	return attrib.Value == "unset" || attrib.Value == "false"
+}
+
 // mergeLanguageStats mergers language names with different cases. The name with most upper case letters is used.
 func mergeLanguageStats(stats map[string]int64) map[string]int64 {
 	names := map[string]struct {