Documentation: Fix build failure of docs.

This patch fixes the build failure due to what seems to be extraneous characters, "+++" in the git-filter-branch.txt file.

$make man

...

ASCIIDOC git-filter-branch.xml
XMLTO git-filter-branch.1
xmlto: input does not validate (status 1) /home/bobthe/git.kernel.org/git/Documentation/git-filter-branch.xml:435:
parser error : PCDATA invalid Char value 7
Clone it with <literal>git clone +++0+++</literal>. The clone

                                    ^
/home/bobthe/git.kernel.org/git/Documentation/git-filter-branch.xml:435:
parser error : PCDATA invalid Char value 7
Clone it with <literal>git clone +++0+++</literal>.  The clone
                                      ^

make[1]: *** [git-filter-branch.1] Error 1
make[1]: Leaving directory
`/home/bobthe/git.kernel.org/git/Documentation'
make: *** [man] Error 2

...

---
 Documentation/git-filter-branch.txt |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

index ab527b5..8a261c7 100644
@@ -364,7 +364,7 @@ objects until you tell it to.  First make sure that:
 Then there are two ways to get a smaller repository.  A safer way is
 to clone, that keeps your original intact.
 
-* Clone it with `git clone +++file:///path/to/repo+++`.  The clone
+* Clone it with `git clone file:///path/to/repo`.  The clone
   will not have the removed objects.  See linkgit:git-clone[1].  (Note
   that cloning with a plain path just hardlinks everything!)
 

1.5.6.3

[...]

NAK. Presumably you are using an asciidoc 8.x? Please check if saying

make ASCIIDOC8=Yes man

fixes the problem. Read the comments in Documentation/Makefile for advice on what precise combination of options you should use. Also, if you do not want to actually work on docs

make quick-install-man

is a much less painful way to get manpages (in this case, from Junio's 'man' branch that has preformatted manpages for 'master').

I put the +++ in there to stop the version I used at the time from rendering the closing backtick as part of the URL and garbling the entire paragraph in the process. To be precise, with asciidoc 8.2.7 and without the +++ I get

Clone it with <tt>git clone <a href="file:///path/to/repo</tt">file:///path/to/repo</tt</a>>.

in the HTML output. Note the nested tags. (With asciidoc 8.4.5 the problem appears to be fixed.)

Thomas Rast
trast@{inf,student}.ethz.ch