Key mapping <Leader>R: Rename vars/functions/classes without deleting the word under the cursor

This pull request also adds the support for 'set selection=exclusive' to
the function 'rename_visual()' (bug fix).

'<Leader>R' in Normal mode:
---------------------------
Jedi-vim keeps the word under the cursor, moves the cursor to the end of the
word, and puts Vim in insert mode, where the user is expected to enter the
new variable name.

'<Leader>R' in Visual mode:
---------------------------
Use the selected text as the default answer to the prompt.

pythonx/jedi_vim.py

@@ -998,7 +998,7 @@ def cmdline_call_signatures(signatures):
 
 @_check_jedi_availability(show_error=True)
 @catch_and_print_exceptions
-def rename():
+def rename(delete_word=True):
     if not int(vim.eval('a:0')):
         # Need to save the cursor position before insert mode
         cursor = vim.current.window.cursor
@@ -1010,7 +1010,12 @@ def rename():
 
         vim_command("let s:jedi_replace_orig = expand('<cword>')")
         line = vim_eval('getline(".")')
-        vim_command('normal! diw')
+
+        if delete_word:
+            vim_command('normal! diw')
+        else:
+            vim_command('normal! yiwel')
+
         if re.match(r'\w+$', line[cursor[1]:]):
             # In case the deleted word is at the end of the line we need to
             # move the cursor to the end.
@@ -1042,9 +1047,17 @@ def rename():
             return do_rename(replace)
 
 
-def rename_visual():
-    replace = vim.eval('input("Rename to: ")')
-    orig = vim.eval('getline(".")[(getpos("\'<")[2]-1):getpos("\'>")[2]]')
+def rename_visual(use_selected_text_as_prompt_answer=False):
+    orig = vim.eval('getline(".")[(getpos("\'<")[2]-1):getpos("\'>")[2]'
+                    '-((&selection ==# "exclusive") ? 2 : 1)]')
+
+    input_text = ""
+    if use_selected_text_as_prompt_answer:
+        input_text = orig
+
+    replace = vim.eval(
+        'input("Rename to:", "{}")'.format(PythonToVimStr(input_text))
+    )
     do_rename(replace, orig)
 
 
@@ -1056,6 +1069,10 @@ def do_rename(replace, orig=None):
     if orig is None:
         orig = vim_eval('s:jedi_replace_orig')
 
+    if orig == replace:
+        echo_highlight('Jedi did 0 renames.')
+        return
+
     # Save original window / tab.
     saved_tab = int(vim_eval('tabpagenr()'))
     saved_win = int(vim_eval('winnr()'))