Use "whitespace" consistently

Most of the messages and documentation use 'whitespace' rather than
'white space' or 'white spaces' convert to latter two to the former for
consistency.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/diff-options.txt

@@ -298,7 +298,7 @@ dimmed-zebra::
 	settings. It is the same as `--color-moved=no`.
 
 --color-moved-ws=<modes>::
-	This configures how white spaces are ignored when performing the
+	This configures how whitespace is ignored when performing the
 	move detection for `--color-moved`.
 ifdef::git-diff[]
 	It can be set by the `diff.colorMovedWS` configuration setting.
@@ -316,7 +316,7 @@ ignore-all-space::
 	Ignore whitespace when comparing lines. This ignores differences
 	even if one line has whitespace where the other line has none.
 allow-indentation-change::
-	Initially ignore any white spaces in the move detection, then
+	Initially ignore any whitespace in the move detection, then
 	group the moved code blocks only into a block if the change in
 	whitespace is the same per line. This is incompatible with the
 	other modes.

Documentation/git-cat-file.txt

@@ -23,8 +23,8 @@ In the second form, a list of objects (separated by linefeeds) is provided on
 stdin, and the SHA-1, type, and size of each object is printed on stdout. The
 output format can be overridden using the optional `<format>` argument. If
 either `--textconv` or `--filters` was specified, the input is expected to
-list the object names followed by the path name, separated by a single white
-space, so that the appropriate drivers can be determined.
+list the object names followed by the path name, separated by a single
+whitespace, so that the appropriate drivers can be determined.
 
 OPTIONS
 -------
@@ -79,7 +79,7 @@ OPTIONS
 	Print object information and contents for each object provided
 	on stdin.  May not be combined with any other options or arguments
 	except `--textconv` or `--filters`, in which case the input lines
-	also need to specify the path, separated by white space.  See the
+	also need to specify the path, separated by whitespace.  See the
 	section `BATCH OUTPUT` below for details.
 
 --batch-check::
@@ -87,7 +87,7 @@ OPTIONS
 	Print object information for each object provided on stdin.  May
 	not be combined with any other options or arguments except
 	`--textconv` or `--filters`, in which case the input lines also
-	need to specify the path, separated by white space.  See the
+	need to specify the path, separated by whitespace.  See the
 	section `BATCH OUTPUT` below for details.
 
 --batch-all-objects::

diff.c

@@ -320,7 +320,7 @@ static int parse_color_moved_ws(const char *arg)
 
 	if ((ret & COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE) &&
 	    (ret & XDF_WHITESPACE_FLAGS))
-		die(_("color-moved-ws: allow-indentation-change cannot be combined with other white space modes"));
+		die(_("color-moved-ws: allow-indentation-change cannot be combined with other whitespace modes"));
 
 	string_list_clear(&l, 0);