Documentation: remove unnecessary backslashes

asciidoctor does not remove backslashes used to escape curly brackets from
the HTML output if the contents of the curly brackets are empty or contain
at least a <, -, or space.  asciidoc does not require the backslashes in
these cases, so just remove them.

Signed-off-by: Matthew Kraai <matt.kraai@abbott.com>
Reported-by: Philip Oakley <philipoakley@iee.org>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/revisions.txt

@@ -61,19 +61,19 @@ some output processing may assume ref names in UTF-8.
 '@'::
   '@' alone is a shortcut for 'HEAD'.
 
-'<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
+'<refname>@{<date>}', e.g. 'master@\{yesterday\}', 'HEAD@{5 minutes ago}'::
   A ref followed by the suffix '@' with a date specification
   enclosed in a brace
-  pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
-  second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
+  pair (e.g. '\{yesterday\}', '{1 month 2 weeks 3 days 1 hour 1
+  second ago}' or '{1979-02-26 18:30:00}') specifies the value
   of the ref at a prior point in time.  This suffix may only be
   used immediately following a ref name and the ref must have an
   existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
   of your *local* ref at a given time; e.g., what was in your local
   'master' branch last week. If you want to look at commits made during
   certain times, see '--since' and '--until'.
 
-'<refname>@\{<n>\}', e.g. 'master@\{1\}'::
+'<refname>@{<n>}', e.g. 'master@\{1\}'::
   A ref followed by the suffix '@' with an ordinal specification
   enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
   the n-th prior value of that ref.  For example 'master@\{1\}'
@@ -82,13 +82,13 @@ some output processing may assume ref names in UTF-8.
   immediately following a ref name and the ref must have an existing
   log ('$GIT_DIR/logs/<refname>').
 
-'@\{<n>\}', e.g. '@\{1\}'::
+'@{<n>}', e.g. '@\{1\}'::
   You can use the '@' construct with an empty ref part to get at a
   reflog entry of the current branch. For example, if you are on
   branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
 
-'@\{-<n>\}', e.g. '@\{-1\}'::
-  The construct '@\{-<n>\}' means the <n>th branch/commit checked out
+'@{-<n>}', e.g. '@{-1}'::
+  The construct '@{-<n>}' means the <n>th branch/commit checked out
   before the current one.
 
 '<branchname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
@@ -139,7 +139,7 @@ from one location and push to another. In a non-triangular workflow,
   '<rev>{caret}1{caret}1{caret}1'.  See below for an illustration of
   the usage of this form.
 
-'<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
+'<rev>{caret}{<type>}', e.g. 'v0.99.8{caret}\{commit\}'::
   A suffix '{caret}' followed by an object type name enclosed in
   brace pair means dereference the object at '<rev>' recursively until
   an object of type '<type>' is found or the object cannot be
@@ -159,13 +159,13 @@ it does not have to be dereferenced even once to get to an object.
 'rev{caret}\{tag\}' can be used to ensure that 'rev' identifies an
 existing tag object.
 
-'<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
+'<rev>{caret}{}', e.g. 'v0.99.8{caret}{}'::
   A suffix '{caret}' followed by an empty brace pair
   means the object could be a tag,
   and dereference the tag recursively until a non-tag object is
   found.
 
-'<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
+'<rev>{caret}{/<text>}', e.g. 'HEAD^{/fix nasty bug}'::
   A suffix '{caret}' to a revision parameter, followed by a brace
   pair that contains a text led by a slash,
   is the same as the ':/fix nasty bug' syntax below except that