Documentation: quote double-dash for AsciiDoc

AsciiDoc versions since 5.0.6 treat a double-dash surrounded by spaces
(outside of verbatim environments) as a request to insert an em dash.
Such versions also treat the three-character sequence "\--", when not
followed by another dash, as a request to insert two literal minus
signs.  Thus from time to time there have been patches to add
backslashes to AsciiDoc markup to escape double-dashes that are meant
to be represent '--' characters used literally on the command line;
see v1.4.0-rc1~174, Fix up docs where "--" isn't displayed correctly,
2006-05-05, for example.

AsciiDoc 6.0.3 (2005-04-20) made life harder by also treating
double-dashes without surrounding whitespace as markup for an em dash,
though only when formatting for backends other than the manpages
(e.g., HTML).  Many pages needed to be changed to use a backslash
before the "--" in names of command-line flags like "--add" (see
v0.99.6~37, Update tutorial, 2005-08-30).

AsciiDoc 8.3.0 (2008-11-29) refined the em-dash rule to avoid that
requirement.  Double-dashes without surrounding spaces are not
rendered as em dashes any more unless bordered on both sides by
alphanumeric characters.  The unescaped markup for option names (e.g.,
"--add") works fine, and many instances of this style have leaked into
Documentation/; git's HTML documentation contains many spurious em
dashes when formatted by an older toolchain.  (This patch will not
change that.)

The upshot: "--" as an isolated word and in phrases like "git
web--browse" must be escaped if it is not to be rendered as an em dash
by current asciidoc.  Use "\--" to avoid such misformatting in
sentences in which "--" represents a literal double-minus command line
argument that separates options and revs from pathspecs, and use
"{litdd}" in cases where the double-dash is embedded in the command
name.  The latter is just for consistency with v1.7.3-rc0~13^2 (Work
around em-dash handling in newer AsciiDoc, 2010-08-23).

List of lines to fix found by grepping manpages for "(em".

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Improved-by: Junio C Hamano <gitster@pobox.com>
Improved-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -676,7 +676,7 @@ branch.<name>.rebase::
 browser.<tool>.cmd::
 	Specify the command to invoke the specified browser. The
 	specified command is evaluated in shell with the URLs passed
-	as arguments. (See linkgit:git-web--browse[1].)
+	as arguments. (See linkgit:git-web{litdd}browse[1].)
 
 browser.<tool>.path::
 	Override the path for the given tool that may be used to

Documentation/git-commit.txt

@@ -275,7 +275,7 @@ When recording your own work, the contents of modified files in
 your working tree are temporarily stored to a staging area
 called the "index" with 'git add'.  A file can be
 reverted back, only in the index but not in the working tree,
-to that of the last commit with `git reset HEAD -- <file>`,
+to that of the last commit with `git reset HEAD \-- <file>`,
 which effectively reverts 'git add' and prevents the changes to
 this file from participating in the next commit.  After building
 the state to be committed incrementally with these commands,

Documentation/git-mergetool--lib.txt

@@ -7,7 +7,7 @@ git-mergetool--lib - Common git merge tool shell scriptlets
 
 SYNOPSIS
 --------
-'TOOL_MODE=(diff|merge) . "$(git --exec-path)/git-mergetool--lib"'
+'TOOL_MODE=(diff|merge) . "$(git --exec-path)/git-mergetool{litdd}lib"'
 
 DESCRIPTION
 -----------

Documentation/git-revert.txt

@@ -23,7 +23,7 @@ throw away all uncommitted changes in your working directory, you
 should see linkgit:git-reset[1], particularly the '--hard' option.  If
 you want to extract specific files as they were in another commit, you
 should see linkgit:git-checkout[1], specifically the `git checkout
-<commit> -- <filename>` syntax.  Take care with these alternatives as
+<commit> \-- <filename>` syntax.  Take care with these alternatives as
 both will discard uncommitted changes in your working directory.
 
 OPTIONS

Documentation/git-submodule.txt

@@ -172,7 +172,7 @@ sync::
 	repositories accordingly.
 +
 "git submodule sync" synchronizes all submodules while
-"git submodule sync -- A" synchronizes submodule "A" only.
+"git submodule sync \-- A" synchronizes submodule "A" only.
 
 OPTIONS
 -------

Documentation/git-web--browse.txt

@@ -68,7 +68,7 @@ browser.<tool>.path
 You can explicitly provide a full path to your preferred browser by
 setting the configuration variable 'browser.<tool>.path'. For example,
 you can configure the absolute path to firefox by setting
-'browser.firefox.path'. Otherwise, 'git web--browse' assumes the tool
+'browser.firefox.path'. Otherwise, 'git web{litdd}browse' assumes the tool
 is available in PATH.
 
 browser.<tool>.cmd

Documentation/rev-list-options.txt

@@ -268,7 +268,7 @@ that you are filtering for a file `foo` in this commit graph:
 	 \   /   /   /   /
 	  `-------------'
 -----------------------------------------------------------------------
-The horizontal line of history A--P is taken to be the first parent of
+The horizontal line of history A---P is taken to be the first parent of
 each merge.  The commits are:
 
 * `I` is the initial commit, in which `foo` exists with contents