Add 'gf' (goto file) functionality

src/file.cc

@@ -185,4 +185,16 @@ void write_buffer_to_file(const Buffer& buffer, const String& filename)
     }
 }
 
+String find_file(const String& filename, const memoryview<String>& paths)
+{
+    for (auto path : paths)
+    {
+        String candidate = path + filename;
+        struct stat buf;
+        if (stat(candidate.c_str(), &buf) == 0 and S_ISREG(buf.st_mode))
+            return candidate;
+    }
+    return "";
+}
+
 }

src/file.hh

@@ -30,6 +30,7 @@ String parse_filename(const String& filename);
 String read_file(const String& filename);
 Buffer* create_buffer_from_file(const String& filename);
 void write_buffer_to_file(const Buffer& buffer, const String& filename);
+String find_file(const String& filename, const memoryview<String>& paths);
 
 }
 

src/main.cc

@@ -93,6 +93,25 @@ void do_go(Context& context)
                 editor.select(buf.iterator_at_line_begin(buf.line_count() - 1), mode);
                 break;
             }
+            case 'f':
+            {
+                String filename = context.editor().selections().back().content();
+                static char forbidden[] = { '\'', '\\', '\0' };
+                for (auto c : forbidden)
+                    if (contains(filename, c))
+                        return;
+
+                std::vector<String> paths = { ""_str, "/usr/include/"_str };
+                const String& buffer_name = context.buffer().name();
+                auto it = find(reversed(buffer_name), '/');
+                if (it != buffer_name.rend())
+                    paths.insert(paths.begin(), String{buffer_name.begin(), it.base()});
+
+                String path = find_file(filename, paths);
+                if (not path.empty())
+                    CommandManager::instance().execute("edit '" + path + "'", context);
+                break;
+            }
             }
         });
 }