Commit: runtime(doc): Clarify list-concatenation a bit more

[Christian Brabandt]

runtime(doc): Clarify list-concatenation a bit more

Commit: https://github.com/vim/vim/commit/c9c2e2d2ff4429a6b5876ee919f15c1dc0018e86
Author: qeatzy <qea...@users.noreply.github.com>
Date: Wed Feb 7 17:52:25 2024 +0100

runtime(doc): Clarify list-concatenation a bit more

Make doc list-concatenation more clear as for += and extend().

1. describe `+=` for list-concatenation more accurately
2. add `extend()` example for list-concatenation
3. Fix CI errors for missing helptags reference |+=|

closes: #13983

Signed-off-by: qeatzy <qea...@users.noreply.github.com>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 75ea2c7f4..3dbbbeafb 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1,4 +1,4 @@
-*eval.txt* For Vim version 9.1. Last change: 2024 Feb 06
+*eval.txt* For Vim version 9.1. Last change: 2024 Feb 07


VIM REFERENCE MANUAL by Bram Moolenaar
@@ -303,7 +303,9 @@ List concatenation ~
*list-concatenation*
Two lists can be concatenated with the "+" operator: >
:let longlist = mylist + [5, 6]
+A list can be concatenated with another one in place using the "+=" operator or |extend()|: >
:let mylist += [7, 8]
+ :call extend(mylist, [7, 8])

To prepend or append an item, turn the item into a list by putting [] around
it. To change a list in-place, refer to |list-modification| below.
@@ -425,7 +427,8 @@ To change part of a list you can specify the first and last item to be
modified. The value must at least have the number of items in the range: >
:let list[3:5] = [3, 4, 5]

-To add items to a List in-place, you can use the |+=| operator: >
+To add items to a List in-place, you can use the += operator
+|list-concatenation|: >
:let listA = [1, 2]
:let listA += [3, 4]
<