patch 9.1.1476: no easy way to deduplicate text

Problem:  no easy way to deduplicate text
Solution: add the :uniq ex command
          (Hirohito Higashi)

closes: #17538

Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index 6bf9e2c..65e4e72 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -1,4 +1,4 @@
-*change.txt*    For Vim version 9.1.  Last change: 2025 May 28
+*change.txt*    For Vim version 9.1.  Last change: 2025 Jun 23
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -20,6 +20,7 @@
 5. Copying and moving text	|copy-move|
 6. Formatting text		|formatting|
 7. Sorting text			|sorting|
+8. Deduplicating text		|deduplicating|
 
 For inserting text see |insert.txt|.
 
@@ -1895,6 +1896,7 @@
 
 Vim has a sorting function and a sorting command.  The sorting function can be
 found here: |sort()|, |uniq()|.
+Also see |:uniq|.
 
 							*:sor* *:sort*
 :[range]sor[t][!] [b][f][i][l][n][o][r][u][x] [/{pattern}/]
@@ -1904,7 +1906,7 @@
 			With [!] the order is reversed.
 
 			With [i] case is ignored.
-
+							*:sort-l*
 			With [l] sort uses the current collation locale.
 			Implementation details: strcoll() is used to compare
 			strings. See |:language| to check or set the collation
@@ -1937,13 +1939,14 @@
 
 			With [b] sorting is done on the first binary number in
 			the line (after or inside a {pattern} match).
-
+							*:sort-u* *:sort-uniq*
 			With [u] (u stands for unique) only keep the first of
 			a sequence of identical lines (ignoring case when [i]
 			is used).  Without this flag, a sequence of identical
 			lines will be kept in their original order.
 			Note that leading and trailing white space may cause
 			lines to be different.
+			When you just want to make things unique, use |:uniq|.
 
 			When /{pattern}/ is specified and there is no [r] flag
 			the text matched with {pattern} is skipped, so that
@@ -1990,4 +1993,56 @@
 process you may end up with duplicated lines.  This also depends on the system
 library function used.
 
+==============================================================================
+8. Deduplicating text				*deduplicating* *unique*
+
+Vim has a deduplicating function and a deduplicating command.  The
+deduplicating function can be found here: |uniq()|.
+Also see |:sort-uniq|.
+
+							*:uni* *:uniq*
+:[range]uni[q][!] [i][l][r][u] [/{pattern}/]
+			Remove duplicate lines that are adjacent to each other
+			in [range].  When no range is given, all lines are
+			processed.
+
+			With [i] case is ignored when comparing lines.
+
+			With [l] comparison uses the current collation locale.
+			See |:sort-l| for more details.
+
+			With [r] comparison is done on the text that matches
+			/{pattern}/ instead of the full line.
+
+			When /{pattern}/ is specified and [r] is not used, the
+			text matched with {pattern} is skipped and comparison
+			is done on what comes after the match.
+			'ignorecase' applies to the pattern, but 'smartcase'
+			is not used.
+
+			Instead of the slash any non-letter can be used.
+
+			For example, to remove adjacent duplicate lines based
+			on the second comma-separated field: >
+				:uniq r /[^,]*,/
+<			Or to keep only unique lines ignoring the first 5
+			characters: >
+				:uniq u /.\{5}/
+<			If {pattern} is empty (e.g. // is used), the last
+			search pattern is used.
+
+			With [u] only keep lines that do not repeat (i.e., are
+			not immediately followed by the same line).
+
+			With [!] only keep lines that are immediately followed
+			by a duplicate.
+
+			If both [!] and [u] are given, [u] is ignored and [!]
+			takes effect.
+
+			Note that leading and trailing white space, and lines
+			that are not adjacent, are not considered duplicates.
+			To remove all duplicates regardless of position, use
+			|:sort-u| or external tools.
+
  vim:tw=78:ts=8:noet:ft=help:norl: