Add "confirmed by gitattributes"

Author: DecimalTurn

README.md

@@ -180,13 +180,25 @@ Ruby:
   …
 ```
 
-If a file's language was overridden using `.gitattributes`, the strategy will show the original detection method along with an override note (fictional example):
+If a file's language is affected by `.gitattributes`, the strategy will show the original detection method along with a note indicating whether the gitattributes setting changed the result or confirmed it.
+
+For instance, if you had the following .gitattributes overrides in your repo:
+
+```gitattributes
+
+*.ts linguist-language=JavaScript
+*.js linguist-language=JavaScript
+
+```
+
+the output of Linguist would be something like this:
 
 ```console
 100.00% 217        JavaScript
 
 JavaScript:
   demo.ts [Heuristics (overridden by .gitattributes)]
+  demo.js [Extension (confirmed by .gitattributes)]
 ```
 
 ##### `--json`
@@ -241,17 +253,30 @@ lib/linguist.rb: 105 lines (96 sloc)
   strategy:  Extension
 ```
 
-If a file's language was overridden using `.gitattributes`, the strategy will show the original detection method along with an override note:
+If a file's language is affected by `.gitattributes`, the strategy will show whether the gitattributes setting changed the result or confirmed it:
 
+In this ficticious example, it says "confirmed by .gitattributes" since the detection process (using the Filename strategy) would have given the same output as the override:
 ```console
-$ github-linguist --strategies .devcontainer/devcontainer.json
 .devcontainer/devcontainer.json: 27 lines (27 sloc)
   type:      Text
   mime type: application/json
   language:  JSON with Comments
-  strategy:  Filename (overridden by .gitattributes)
+  strategy:  Filename (confirmed by .gitattributes)
 ```
 
+In this other example, it says "overridden by .gitattributes" since the gitattributes setting changes the detected language to something different:
+
+```console
+$ github-linguist --strategies test/attributes/test.rb
+test/attributes/test.rb: 13 lines (11 sloc)
+  type:      Text
+  mime type: application/x-ruby
+  language:  Java
+  strategy:  Extension (overridden by .gitattributes)
+```
+
+Here, the `.rb` file would normally be detected as Ruby by the Extension strategy, but `.gitattributes` overrides it to be detected as Java instead.
+
 ##### `--json`
 
 Using the `--json` flag will give you the output for a single file in JSON format:

lib/linguist/lazy_blob.rb

@@ -75,14 +75,19 @@ def language
       @language = if lang = git_attributes['linguist-language']
         detected_language = Language.find_by_alias(lang)
 
-        # If strategies are being tracked, get the overridden strategy that would have been used with a note that it was overridden
+        # If strategies are being tracked, get the original strategy that would have been used
         if detected_language && Linguist.instrumenter
-          # Get the overridden strategy by calling super (which calls Linguist.detect)
-          super
-          overridden_strategy_info = Linguist.instrumenter.detected_info[self.name]
-          overridden_strategy = overridden_strategy_info ? overridden_strategy_info[:strategy] : "Unknown"
+          # Get the original strategy by calling super (which calls Linguist.detect)
+          original_language = super
+          original_strategy_info = Linguist.instrumenter.detected_info[self.name]
+          original_strategy = original_strategy_info ? original_strategy_info[:strategy] : "Unknown"
+
+          if original_language == detected_language
+            strategy_name = "#{original_strategy} (confirmed by .gitattributes)"
+          else
+            strategy_name = "#{original_strategy} (overridden by .gitattributes)"
+          end
 
-          strategy_name = "#{overridden_strategy} (overridden by .gitattributes)"
           strategy = Struct.new(:name).new(strategy_name)
           Linguist.instrument("linguist.detected", blob: self, strategy: strategy, language: detected_language)
         end