docs(help): specify h4 "function signature" format #42434master

Work towards enabling ["flow" layout](https://github.com/neovim/neovim/blob/9244da12e400ec0291450a5e9400d995e7a29b83/src/gen/gen_help_html.lua#L86-L88)
in all `:help` files.

Problem:
The final boss of vimdoc pseudo-structure: Vim's quasi-headings on
function signatures and excmd docs is visually distinctive but too
inconsistent for a nice parse rule.

Solution:
- Define the quasi-heading format as an "h4" variant, specified at
  `:help help-tag-heading`.
  - For simplicity and predictability, it is defined as any line that
    ends with a help tag(s) preceded by 2 or more spaces (or 1 tab).
- Update existing docs.
  - This one-time update has a lot of changes, but is very unlikely to
    conflict with ported Vim-patches because (1) Vim rarely adds new
    *excmds* that we want, and (2) *function* docs are auto-generated.

ref https://github.com/neovim/tree-sitter-vimdoc/issues/110

1 files changed, 29 insertions, 23 deletions

diff --git a/runtime/doc/starting.txt b/runtime/doc/starting.txt
index 802d7b56cc..90e43bb2a1 100644
--- a/runtime/doc/starting.txt
+++ b/runtime/doc/starting.txt
@@ -34,8 +34,8 @@ filename        One or more file names.  The first one will be the current
 <                All arguments after "--" are interpreted as file names, no
                 other options or "+command" arguments can follow.
 
-                                                        *--*
-`-`               Alias for stdin (standard input).
+`-`                                                     *--*
+                Alias for stdin (standard input).
                 Example: >
                         echo text | nvim - file
 <                "text" is read into buffer 1, "file" is opened as buffer 2.
@@ -79,16 +79,18 @@ The option arguments may be given in any order.  Single-letter options can be
 combined after one dash.  There can be no option arguments after the "--"
 argument.
 
---help                                                  *-h* *--help* *-?*
--?
--h              Give usage (help) message and exit.
+--help                                                  *--help*
+-?                                                      *-?*
+-h                                                      *-h*
+                Give usage (help) message and exit.
 
---version                                               *-v* *--version*
--v              Print version information and exit.  Same output as for
+--version                                               *--version*
+-v                                                      *-v*
+                Print version information and exit.  Same output as for
                 |:version| command.
 
-                                                        *--clean*
---clean         Mimics a fresh install of Nvim:
+--clean                                                 *--clean*
+                Mimics a fresh install of Nvim:
                 - Skips initializations from files and environment variables.
                 - No 'shada' file is read or written.
                 - Excludes user directories from 'runtimepath'
@@ -122,8 +124,9 @@ argument.
                 last used from |shada|.  To force a search from the first
                 line use "+1 +/pat".
 
-+{command}                                              *-+c* *-c*
--c {command}    {command} will be executed after the first file has been
++{command}                                              *-+c*
+-c {command}                                            *-c*
+                {command} will be executed after the first file has been
                 read (and after autocommands and modelines for that file have
                 been processed).  "command" is interpreted as an Ex command.
                 If the "command" contains spaces, it must be enclosed in
@@ -150,8 +153,9 @@ argument.
 <                Can be repeated like "-c", subject to the same limit of 10
                 "-c" arguments. {file} cannot start with a "-".
 
--L                                                      *-L* *-r*
--r              Recovery mode.  Without a file name argument, a list of
+-L                                                      *-L*
+-r                                                      *-r*
+                Recovery mode.  Without a file name argument, a list of
                 existing swap files is given.  With a file name, a swap file
                 is read to recover a crashed editing session.  See
                 |crash-recovery|.
@@ -181,15 +185,17 @@ argument.
                 the 'modifiable' and 'write' options can be set to enable
                 changes and writing.
 
--e                                                      *-e* *-E*
--E              Start Nvim in |Ex-mode|.
+-e                                                      *-e*
+-E                                                      *-E*
+                Start Nvim in |Ex-mode|.
 
                 If stdin is not a TTY:
                 • -e reads/executes stdin as Ex commands.
                 • -E reads stdin as text (into buffer 1).
 
--es                                             *-es* *-Es* *-s-ex* *silent-mode*
--Es             Script mode, aka "silent mode", aka "batch mode". No UI,
+-es                                                     *-es* *-s-ex* *silent-mode*
+-Es                                                     *-Es*
+                Script mode, aka "silent mode", aka "batch mode". No UI,
                 disables most prompts and messages. Unrelated to |-s|.
                 See also |-S| to run script files.
 
@@ -219,8 +225,7 @@ argument.
                 Disables |shada| unless |-i| was given.
                 Disables swapfile (like |-n|).
 
-                                                        *-l*
--l {script} [args]
+-l {script} [args]                                      *-l*
                 Executes Lua {script} non-interactively (no UI) with optional
                 [args] after processing any preceding Nvim |cli-arguments|,
                 then exits. Exits 1 on Lua error. See |-S| to run multiple Lua
@@ -686,15 +691,16 @@ greps in the help files) you might be able to use this: >
 ==============================================================================
 Suspending                                              *suspend*
 
-                                        *CTRL-Z* *v_CTRL-Z*
-CTRL-Z                  Suspend Nvim, like ":stop".
+CTRL-Z                                                  *CTRL-Z* *v_CTRL-Z*
+                        Suspend Nvim, like ":stop".
                         Works in Normal and in Visual mode.  In Insert and
                         Command-line mode, the CTRL-Z is inserted as a normal
                         character.  In Visual mode Nvim goes back to Normal
                         mode before suspending.
 
-:sus[pend][!]   or                      *:sus* *:suspend* *:st* *:stop*
-:st[op][!]              Suspend Nvim using OS "job control"; it will continue
+:sus[pend][!]                                           *:sus* *:suspend*
+:st[op][!]                                              *:st* *:stop*
+                        Suspend Nvim using OS "job control"; it will continue
                         if you make it the foreground job again.  Triggers
                         |VimSuspend| before suspending and |VimResume| when
                         resumed.