Support % in path option to mean current buffer directory

In the end, % is not that painful to work with as its only set seldomly,
and we usually dont need to use expansion at the same time. Moreover, it
just requires a single \ to be escaped.

Fixes #1562

src/file.cc

@@ -48,14 +48,21 @@ public:
         : runtime_error(format("fd {}: {}", fd, error_desc)) {}
 };
 
-String parse_filename(StringView filename)
+String parse_filename(StringView filename, StringView buf_dir)
 {
     auto prefix = filename.substr(0_byte, 2_byte);
     if (prefix == "~" or prefix == "~/")
         return homedir() + filename.substr(1_byte);
+    if ((prefix == "%" or prefix == "%/") and not buf_dir.empty())
+        return buf_dir + filename.substr(1_byte);
     return filename.str();
 }
 
+String parse_filename(StringView filename)
+{
+    return parse_filename(filename, {});
+}
+
 std::pair<StringView, StringView> split_path(StringView path)
 {
     auto it = find(path | reverse(), '/');
@@ -331,7 +338,7 @@ void write_buffer_to_backup_file(Buffer& buffer)
     }
 }
 
-String find_file(StringView filename, ConstArrayView<String> paths)
+String find_file(StringView filename, StringView buf_dir, ConstArrayView<String> paths)
 {
     struct stat buf;
     if (filename.substr(0_byte, 1_byte) == "/")
@@ -348,7 +355,7 @@ String find_file(StringView filename, ConstArrayView<String> paths)
         return "";
     }
 
-    for (auto candidate : paths | transform(parse_filename))
+    for (auto candidate : paths | transform([&](StringView s) { return parse_filename(s, buf_dir); }))
     {
         if (not candidate.empty() and candidate.back() != '/')
             candidate += '/';

src/file.hh

@@ -19,8 +19,10 @@ class Regex;
 
 using CandidateList = Vector<String, MemoryDomain::Completion>;
 
-// parse ~/ and $env values in filename and returns the translated filename
+// parse ~/ and %/ in filename and returns the translated filename
+String parse_filename(StringView filename, StringView buf_dir);
 String parse_filename(StringView filename);
+
 String real_path(StringView filename);
 String compact_path(StringView filename);
 
@@ -54,7 +56,7 @@ void write_buffer_to_file(Buffer& buffer, StringView filename, bool force = fals
 void write_buffer_to_fd(Buffer& buffer, int fd);
 void write_buffer_to_backup_file(Buffer& buffer);
 
-String find_file(StringView filename, ConstArrayView<String> paths);
+String find_file(StringView filename, StringView buf_dir, ConstArrayView<String> paths);
 bool file_exists(StringView filename);
 
 Vector<String> list_files(StringView directory);

src/insert_completer.cc

@@ -246,6 +246,13 @@ InsertCompletion complete_filename(const SelectionList& sels,
         {
             if (not dir.empty() and dir.back() != '/')
                 dir += '/';
+            if (dir.substr(0, 2_byte) == "%/")
+            {
+                if (not (buffer.flags() & Buffer::Flags::File))
+                    continue;
+                dir = split_path(buffer.name()).first.str() + '/' + dir.substr(2_byte);
+            }
+
             for (auto& filename : Kakoune::complete_filename(dir + prefix,
                                                              options["ignored_files"].get<Regex>()))
             {

src/main.cc

@@ -323,7 +323,7 @@ void register_options()
                       Regex{});
     reg.declare_option("filetype", "buffer filetype", ""_str);
     reg.declare_option("path", "path to consider when trying to find a file",
-                   Vector<String, MemoryDomain::Options>({ "./", "/usr/include" }));
+                   Vector<String, MemoryDomain::Options>({ "./", "%/", "/usr/include" }));
     reg.declare_option("completers", "insert mode completers to execute.",
                        InsertCompleterDescList({
                            InsertCompleterDesc{ InsertCompleterDesc::Filename, {} },

src/normal.cc

@@ -278,11 +278,8 @@ void goto_commands(Context& context, NormalParams params)
                     return;
 
                 auto paths = context.options()["path"].get<Vector<String, MemoryDomain::Options>>();
-                StringView buffer_dir = split_path(buffer.name()).first;
-                if (not buffer_dir.empty())
-                    paths.insert(paths.begin(), buffer_dir.str());
-
-                String path = find_file(filename, paths);
+                const StringView buffer_dir = split_path(buffer.name()).first;
+                String path = find_file(filename, buffer_dir, paths);
                 if (path.empty())
                     throw runtime_error(format("unable to find file '{}'", filename));