Fix crash when running copy -bik and also clean up cmd_copy()

Reproducer:

* Start `dte`
* Insert a few characters
* Run `copy -bik`

Result:

> src/block-iter.c:356: **BUG** in block_iter_get_bytes():
> 'pos < len && blk->node.next == bi->head'
>
> Stack trace:
>   #0 0x721e6a90bdd8 in __sanitizer_print_stack_trace asan_stack.cpp:87
>   #1 0x5fe2730bb194 in print_stack_trace src/util/debug.c:67
>   #2 0x5fe2730bb72f in bug src/util/debug.c:86
>   #3 0x5fe272fe0d43 in block_iter_get_bytes src/block-iter.c:356
>   #4 0x5fe27300516b in cmd_copy src/commands.c:509
>   #5 0x5fe272fdcc8a in command_func_call src/command/run.h:74
>   #6 0x5fe272fdd29d in handle_binding src/bind.c:51
>   #7 0x5fe27304acef in handle_input_single src/mode.c:80
>   #8 0x5fe27304b08a in handle_input_recursive src/mode.c:89
>   #9 0x5fe27304b311 in handle_input src/mode.c:106
>   #10 0x5fe273023a01 in main_loop src/editor.c:338
>   #11 0x5fe273049b0f in main src/main.c:663
>   #12 0x721e69e34e07  (/usr/lib/libc.so.6+0x25e07)
>   #13 0x721e69e34ecb in __libc_start_main (/usr/lib/libc.so.6+0x25ecb)
>   #14 0x5fe272fdcb24 in _start (dte/dte+0x16bb24)

Thanks to Pedro Navarro for the bug report!

src/commands.c

@@ -477,16 +477,19 @@ static bool cmd_copy(EditorState *e, const CommandArgs *a)
         return true;
     }
 
-    View *view = e->view;
-    const BlockIter save = view->cursor;
+    const View *view = e->view;
+    BlockIter bi;
     size_t size;
     bool line_copy;
     if (view->selection) {
-        size = prepare_selection(view);
+        SelectionInfo info = init_selection(view);
+        size = info.eo - info.so;
+        bi = info.si;
         line_copy = (view->selection == SELECT_LINES);
     } else {
-        block_iter_bol(&view->cursor);
-        BlockIter tmp = view->cursor;
+        bi = view->cursor;
+        block_iter_bol(&bi);
+        BlockIter tmp = bi;
         size = block_iter_eat_line(&tmp);
         line_copy = true;
     }
@@ -495,29 +498,24 @@ static bool cmd_copy(EditorState *e, const CommandArgs *a)
         return true;
     }
 
-    if (internal) {
-        copy(&e->clipboard, view, size, line_copy);
-    }
-
+    char *buf = block_iter_get_bytes(&bi, size);
     if (osc52) {
-        if (internal) {
-            view->cursor = save;
-            if (view->selection) {
-                size = prepare_selection(view);
-            }
-        }
-        char *buf = block_iter_get_bytes(&view->cursor, size);
         if (!term_osc52_copy(&term->obuf, buf, size, clipboard, primary)) {
             error_msg_errno(e->err, "OSC 52 copy failed");
         }
+    }
+
+    if (internal) {
+        // Clipboard takes ownership of `buf`
+        record_copy(&e->clipboard, buf, size, line_copy);
+    } else {
         free(buf);
     }
 
     if (!has_flag(a, 'k')) {
-        unselect(view);
+        unselect(e->view);
     }
 
-    view->cursor = save;
     // TODO: return false if term_osc52_copy() failed?
     return true;
 }

src/copy.c

@@ -16,18 +16,11 @@ void record_copy(Clipboard *clip, char *buf, size_t len, bool is_lines)
     clip->is_lines = is_lines;
 }
 
-void copy(Clipboard *clip, View *view, size_t len, bool is_lines)
+void cut(Clipboard *clip, View *view, size_t len, bool is_lines)
 {
     if (len) {
         char *buf = block_iter_get_bytes(&view->cursor, len);
         record_copy(clip, buf, len, is_lines);
-    }
-}
-
-void cut(Clipboard *clip, View *view, size_t len, bool is_lines)
-{
-    if (len) {
-        copy(clip, view, len, is_lines);
         buffer_delete_bytes(view, len);
     }
 }

src/copy.h

@@ -19,7 +19,6 @@ typedef enum {
 } PasteLinesType;
 
 void record_copy(Clipboard *clip, char *buf, size_t len, bool is_lines);
-void copy(Clipboard *clip, View *view, size_t len, bool is_lines);
 void cut(Clipboard *clip, View *view, size_t len, bool is_lines);
 void paste(Clipboard *clip, View *view, PasteLinesType type, bool move_after);