Update documentation for stripspace

Tell the user what this command is intended for, and expand the
description of what it does.

Signed-off-by: Conrad Irwin <conrad.irwin@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-stripspace.txt

@@ -3,26 +3,83 @@ git-stripspace(1)
 
 NAME
 ----
-git-stripspace - Filter out empty lines
+git-stripspace - Remove unnecessary whitespace
 
 
 SYNOPSIS
 --------
 [verse]
-'git stripspace' [-s | --strip-comments] < <stream>
+'git stripspace' [-s | --strip-comments] < input
 
 DESCRIPTION
 -----------
-Remove multiple empty lines, and empty lines at beginning and end.
+
+Clean the input in the manner used by 'git' for text such as commit
+messages, notes, tags and branch descriptions.
+
+With no arguments, this will:
+
+- remove trailing whitespace from all lines
+- collapse multiple consecutive empty lines into one empty line
+- remove empty lines from the beginning and end of the input
+- add a missing '\n' to the last line if necessary.
+
+In the case where the input consists entirely of whitespace characters, no
+output will be produced.
+
+*NOTE*: This is intended for cleaning metadata, prefer the `--whitespace=fix`
+mode of linkgit:git-apply[1] for correcting whitespace of patches or files in
+the repository.
 
 OPTIONS
 -------
 -s::
 --strip-comments::
-	In addition to empty lines, also strip lines starting with '#'.
+	Skip and remove all lines starting with '#'.
+
+EXAMPLES
+--------
+
+Given the following noisy input with '$' indicating the end of a line:
 
-<stream>::
-	Byte stream to act on.
+--------
+|A brief introduction   $
+|   $
+|$
+|A new paragraph$
+|# with a commented-out line    $
+|explaining lots of stuff.$
+|$
+|# An old paragraph, also commented-out. $
+|      $
+|The end.$
+|  $
+---------
+
+Use 'git stripspace' with no arguments to obtain:
+
+--------
+|A brief introduction$
+|$
+|A new paragraph$
+|# with a commented-out line$
+|explaining lots of stuff.$
+|$
+|# An old paragraph, also commented-out.$
+|$
+|The end.$
+---------
+
+Use 'git stripspace --strip-comments' to obtain:
+
+--------
+|A brief introduction$
+|$
+|A new paragraph$
+|explaining lots of stuff.$
+|$
+|The end.$
+---------
 
 GIT
 ---

builtin/stripspace.c

@@ -75,7 +75,7 @@ int cmd_stripspace(int argc, const char **argv, const char *prefix)
 				!strcmp(argv[1], "--strip-comments")))
 		strip_comments = 1;
 	else if (argc > 1)
-		usage("git stripspace [-s | --strip-comments] < <stream>");
+		usage("git stripspace [-s | --strip-comments] < input");
 
 	if (strbuf_read(&buf, 0, 1024) < 0)
 		die_errno("could not read the input");