Add -timestamp switch support to the select command

Fixes #2829

src/commands.cc

@@ -2250,13 +2250,18 @@ const CommandDesc select_cmd = {
     "select <selection_desc>...: select given selections\n"
     "\n"
     "selection_desc format is <anchor_line>.<anchor_column>,<cursor_line>.<cursor_column>",
-    ParameterDesc{{}, ParameterDesc::Flags::SwitchesAsPositional, 1},
+    ParameterDesc{
+        {{"timestamp", {true, "specify buffer timestamp at which those selections are valid"}}},
+        ParameterDesc::Flags::SwitchesOnlyAtStart, 1
+    },
     CommandFlags::None,
     CommandHelper{},
     CommandCompleter{},
     [](const ParametersParser& parser, Context& context, const ShellContext&)
     {
-        context.selections_write_only() = selection_list_from_string(context.buffer(), parser.positionals_from(0));
+        auto& buffer = context.buffer();
+        const size_t timestamp = parser.get_switch("timestamp").map(str_to_int_ifp).cast<size_t>().value_or(buffer.timestamp());
+        context.selections_write_only() = selection_list_from_string(buffer, parser.positionals_from(0), timestamp);
     }
 };
 

src/selection.cc

@@ -516,14 +516,14 @@ Selection selection_from_string(StringView desc)
     return Selection{anchor, cursor};
 }
 
-SelectionList selection_list_from_string(Buffer& buffer, ConstArrayView<String> descs)
+SelectionList selection_list_from_string(Buffer& buffer, ConstArrayView<String> descs, size_t timestamp)
 {
     if (descs.empty())
         throw runtime_error{"empty selection description"};
 
     auto sels = descs | transform([&](auto&& d) { auto s = selection_from_string(d); clamp(s, buffer); return s; })
                       | gather<Vector<Selection>>();
-    return {SelectionList::UnsortedTag{}, buffer, std::move(sels), buffer.timestamp(), 0};
+    return {SelectionList::UnsortedTag{}, buffer, std::move(sels), timestamp, 0};
 }
 
 }

src/selection.hh

@@ -163,7 +163,7 @@ Vector<Selection> compute_modified_ranges(Buffer& buffer, size_t timestamp);
 String selection_to_string(const Selection& selection);
 String selection_list_to_string(const SelectionList& selection);
 Selection selection_from_string(StringView desc);
-SelectionList selection_list_from_string(Buffer& buffer, ConstArrayView<String> descs);
+SelectionList selection_list_from_string(Buffer& buffer, ConstArrayView<String> descs, size_t timestamp);
 
 }
 

test/compose/select-timestamp/cmd

@@ -0,0 +1 @@
+jxd:select -timestamp 1 3.1,3.2<ret>

test/compose/select-timestamp/in

@@ -0,0 +1,4 @@
+aa
+bb
+cc
+dd

test/compose/select-timestamp/selections

@@ -0,0 +1 @@
+'cc'