patch 9.1.1252: typos in code and docs related to 'diffopt' "inline:"

Problem:  Typos in code and docs related to 'diffopt' "inline:".
          (after v9.1.1243)
Solution: Fix typos and slightly improve the docs.
          (zeertzjq)

closes: #16997

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/diff.txt b/runtime/doc/diff.txt
index 0dbc7f8..069a853 100644
--- a/runtime/doc/diff.txt
+++ b/runtime/doc/diff.txt
@@ -1,4 +1,4 @@
-*diff.txt*      For Vim version 9.1.  Last change: 2024 Mar 26
+*diff.txt*      For Vim version 9.1.  Last change: 2024 Mar 28
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -243,12 +243,11 @@
 				highlight the exact difference between the
 				two.  Will respect any 'diffopt' flag that
 				affects internal diff.
-				Not used when `inline:` set to "none".
-|hl-DiffTextAdd|  DiffTextAdd	Added text inside a Changed line. Similar to
+				Not used when `inline:` is set to "none".
+|hl-DiffTextAdd|  DiffTextAdd	Added text inside a Changed line.  Similar to
 				DiffText, but used when there is no
-				corresponding text in other buffers.  Will not
-				be used when `inline:` is set to "simple" or
-				"none".
+				corresponding text in other buffers.  Not used
+				when `inline:` is set to "simple" or "none".
 |hl-DiffDelete|	DiffDelete	Deleted lines.  Also called filler lines,
 				because they don't really exist in this
 				buffer.
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 0b7ba91..84deeca 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 Mar 27
+*options.txt*	For Vim version 9.1.  Last change: 2025 Mar 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2982,8 +2982,8 @@
 				none    Do not perform inline highlighting.
 				simple  Highlight from first different
 					character to the last one in each
-					line. This is the default if nothing
-					is set.
+					line.  This is the default if no
+					`inline:` value is set.
 				char    Use internal diff to perform a
 					character-wise diff and highlight the
 					difference.
diff --git a/src/structs.h b/src/structs.h
index 33c26dc..0baf543 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -3606,7 +3606,7 @@
 struct diffline_change_S
 {
     colnr_T	dc_start[DB_COUNT];	// byte offset of start of range in the line
-    colnr_T	dc_end[DB_COUNT];	// 1 paste byte offset of end of range in line
+    colnr_T	dc_end[DB_COUNT];	// 1 past byte offset of end of range in line
     int		dc_start_lnum_off[DB_COUNT];	// starting line offset
     int		dc_end_lnum_off[DB_COUNT];	// end line offset
 };
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index 6c87da9..1b5e5c0 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ
diff --git a/src/version.c b/src/version.c
index a40a187..cceb83c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1252,
+/**/
     1251,
 /**/
     1250,