main.c: "BufReadCmd term://": Skip existing terminal.

Check `exists('b:term_title')` to avoid the BufReadCmd for already-initialized
:terminal buffers.

Move the test for `:argadd`.
Add a test for `:edit<CR>`.
Tweak comments and code style.

src/nvim/buffer.c

@@ -276,30 +276,25 @@ bool buf_valid(buf_T *buf)
   return false;
 }
 
-/*
- * Close the link to a buffer.
- * "action" is used when there is no longer a window for the buffer.
- * It can be:
- * 0			buffer becomes hidden
- * DOBUF_UNLOAD		buffer is unloaded
- * DOBUF_DELETE		buffer is unloaded and removed from buffer list
- * DOBUF_WIPE		buffer is unloaded and really deleted
- * When doing all but the first one on the current buffer, the caller should
- * get a new buffer very soon!
- *
- * The 'bufhidden' option can force freeing and deleting.
- *
- * When "abort_if_last" is TRUE then do not close the buffer if autocommands
- * cause there to be only one window with this buffer.  e.g. when ":quit" is
- * supposed to close the window but autocommands close all other windows.
- */
-void 
-close_buffer (
-    win_T *win,               /* if not NULL, set b_last_cursor */
-    buf_T *buf,
-    int action,
-    int abort_if_last
-)
+/// Close the link to a buffer.
+///
+/// @param win    If not NULL, set b_last_cursor.
+/// @param buf
+/// @param action Used when there is no longer a window for the buffer.
+///               Possible values:
+///                 0            buffer becomes hidden
+///                 DOBUF_UNLOAD buffer is unloaded
+///                 DOBUF_DELETE buffer is unloaded and removed from buffer list
+///                 DOBUF_WIPE   buffer is unloaded and really deleted
+///               When doing all but the first one on the current buffer, the
+///               caller should get a new buffer very soon!
+///               The 'bufhidden' option can force freeing and deleting.
+/// @param abort_if_last
+///               If TRUE, do not close the buffer if autocommands cause
+///               there to be only one window with this buffer. e.g. when
+///               ":quit" is supposed to close the window but autocommands
+///               close all other windows.
+void close_buffer(win_T *win, buf_T *buf, int action, int abort_if_last)
 {
   bool unload_buf = (action != 0);
   bool del_buf = (action == DOBUF_DEL || action == DOBUF_WIPE);

src/nvim/edit.c

@@ -1286,10 +1286,9 @@ bool edit(int cmdchar, bool startln, long count)
 {
   if (curbuf->terminal) {
     if (ex_normal_busy) {
-      // don't enter terminal mode from `ex_normal`, which can result in all
-      // kinds of havoc(such as terminal mode recursiveness). Instead, set a
-      // flag that allow us to force-set the value of `restart_edit` before
-      // `ex_normal` returns
+      // Do not enter terminal mode from ex_normal(), which would cause havoc
+      // (such as terminal-mode recursiveness). Instead set a flag to force-set
+      // the value of `restart_edit` before `ex_normal` returns.
       restart_edit = 'i';
       force_restart_edit = true;
     } else {

src/nvim/ex_cmds.c

@@ -2116,14 +2116,12 @@ do_ecmd (
     }
   }
 
-  // Make re-editing a terminal buffer a no-op
-  if (!other_file && curbuf->terminal != NULL) {
-      // this is needed for when we are called by do_argfile() and the new
-      // argument index becomes the terminal buffer we are already editing
-      check_arg_idx(curwin);
-      maketitle();
-      retval = OK;
-      goto theend;
+  // Re-editing a terminal buffer: skip most buffer re-initialization.
+  if (!other_file && curbuf->terminal) {
+    check_arg_idx(curwin);  // Needed when called from do_argfile().
+    maketitle();            // Title may show the arg index, e.g. "(2 of 5)".
+    retval = OK;
+    goto theend;
   }
 
   /*

src/nvim/ex_docmd.c

@@ -7916,9 +7916,8 @@ static void ex_normal(exarg_T *eap)
   if (force_restart_edit) {
     force_restart_edit = false;
   } else {
-    // some function called was aware of ex_normal and decided to override the
-    // value of restart_edit anyway. So far only used in terminal mode(see
-    // terminal_enter() in edit.c)
+    // Some function (terminal_enter()) was aware of ex_normal and decided to
+    // override the value of restart_edit anyway.
     restart_edit = save_restart_edit;
   }
   p_im = save_insertmode;

src/nvim/main.c

@@ -320,14 +320,18 @@ int main(int argc, char **argv)
 
   // open terminals when opening files that start with term://
 #define PROTO "term://"
+  do_cmdline_cmd("augroup nvim_terminal");
+  do_cmdline_cmd("autocmd!");
   do_cmdline_cmd("autocmd BufReadCmd " PROTO "* nested "
-                 ":call termopen( "
+                 ":if !exists('b:term_title')|call termopen( "
                  // Capture the command string
                  "matchstr(expand(\"<amatch>\"), "
                  "'\\c\\m" PROTO "\\%(.\\{-}//\\%(\\d\\+:\\)\\?\\)\\?\\zs.*'), "
                  // capture the working directory
                  "{'cwd': get(matchlist(expand(\"<amatch>\"), "
-                 "'\\c\\m" PROTO "\\(.\\{-}\\)//'), 1, '')})");
+                 "'\\c\\m" PROTO "\\(.\\{-}\\)//'), 1, '')})"
+                 "|endif");
+  do_cmdline_cmd("augroup END");
 #undef PROTO
 
   /* Execute --cmd arguments. */