Show the first few history entries in set | grep history

As before, but do so efficiently. See #6290

src/builtin_set.cpp

@@ -482,8 +482,12 @@ static int builtin_set_list(const wchar_t *cmd, set_cmd_opts_t &opts, int argc,
 
         if (!names_only) {
             wcstring val;
-            if (key == L"history") {
-                val = history_variable_description;
+            if (opts.shorten_ok && key == L"history") {
+                history_t *history = &history_t::history_with_name(history_session_id(env_stack_t::principal()));
+                for (size_t i = 1; i < history->size() && val.size() < 64; i++) {
+                    if (i > 1) val += L' ';
+                    val += expand_escape_string(history->item_at_index(i).str());
+                }
             } else {
                 auto var = parser.vars().get(key, compute_scope(opts));
                 if (!var.missing_or_empty()) {

src/complete.cpp

@@ -1193,9 +1193,13 @@ bool completer_t::complete_variable(const wcstring &str, size_t start_offset) {
         wcstring desc;
         if (this->wants_descriptions()) {
             if (this->type() != COMPLETE_AUTOSUGGEST) {
-                // $history can be huge, don't put it in the completion description; see #6288.
+                // $history can be huge, don't put all of it in the completion description; see #6288.
                 if (env_name == L"history") {
-                    desc = history_variable_description;
+                    history_t *history = &history_t::history_with_name(history_session_id(env_stack_t::principal()));
+                    for (size_t i = 1; i < history->size() && desc.size() < 64; i++) {
+                        if (i > 1) desc += L' ';
+                        desc += expand_escape_string(history->item_at_index(i).str());
+                    }
                 } else {
                     // Can't use this->vars here, it could be any variable.
                     auto var = vars.get(env_name);

src/expand.cpp

@@ -145,6 +145,19 @@ wcstring expand_escape_variable(const env_var_t &var) {
     return buff;
 }
 
+wcstring expand_escape_string(const wcstring &el) {
+    wcstring buff;
+    bool prefer_quotes = el.find(L' ') != wcstring::npos;
+    if (prefer_quotes && is_quotable(el)) {
+        buff.append(L"'");
+        buff.append(el);
+        buff.append(L"'");
+    } else {
+        buff.append(escape_string(el, 1));
+    }
+    return buff;
+}
+
 /// Parse an array slicing specification Returns 0 on success. If a parse error occurs, returns the
 /// index of the bad token. Note that 0 can never be a bad index because the string always starts
 /// with [.

src/expand.h

@@ -164,6 +164,10 @@ expand_result_t expand_to_command_and_args(const wcstring &instr, const environm
 /// Suitable for pretty-printing.
 wcstring expand_escape_variable(const env_var_t &var);
 
+/// Convert a string value to a human readable form, i.e. escape things, handle arrays, etc.
+/// Suitable for pretty-printing.
+wcstring expand_escape_string(const wcstring &str);
+
 /// Perform tilde expansion and nothing else on the specified string, which is modified in place.
 ///
 /// \param input the string to tilde expand

src/history.h

@@ -294,8 +294,4 @@ void start_private_mode();
 /// Queries private mode status.
 bool in_private_mode();
 
-/// The description of the $history environment variable, as offered in completions and
-/// the output of builtin set.
-constexpr const wchar_t *history_variable_description = L"Full history of interactive commands";
-
 #endif