Merge branch 'dl/rev-tilde-doc-clarify'

Docfix.

* dl/rev-tilde-doc-clarify:
  revisions.txt: remove ambibuity between <rev>:<path> and :<path>
  revisions.txt: mention <rev>~ form
  revisions.txt: mark optional rev arguments with []
  revisions.txt: change "rev" to "<rev>"

Documentation/revisions.txt

@@ -65,7 +65,7 @@ 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
@@ -95,7 +95,7 @@ some output processing may assume ref names in UTF-8.
   The construct '@{-<n>}' means the <n>th branch/commit checked out
   before the current one.
 
-'<branchname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
+'[<branchname>]@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
   The suffix '@\{upstream\}' to a branchname (short form '<branchname>@\{u\}')
   refers to the branch that the branch specified by branchname is set to build on
   top of (configured with `branch.<name>.remote` and
@@ -103,7 +103,7 @@ some output processing may assume ref names in UTF-8.
   current one. These suffixes are also accepted when spelled in uppercase, and
   they mean the same thing no matter the case.
 
-'<branchname>@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
+'[<branchname>]@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
   The suffix '@\{push}' reports the branch "where we would push to" if
   `git push` were run while `branchname` was checked out (or the current
   `HEAD` if no branchname is specified). Since our push destination is
@@ -131,7 +131,7 @@ from one location and push to another. In a non-triangular workflow,
 This suffix is also accepted when spelled in uppercase, and means the same
 thing no matter the case.
 
-'<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
+'<rev>{caret}[<n>]', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
   A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   '<rev>{caret}'
@@ -139,7 +139,9 @@ thing no matter the case.
   '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
   object name of a tag object that refers to a commit object.
 
-'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
+'<rev>{tilde}[<n>]', e.g. 'HEAD{tilde}, master{tilde}3'::
+  A suffix '{tilde}' to a revision parameter means the first parent of
+  that commit object.
   A suffix '{tilde}<n>' to a revision parameter means the commit
   object that is the <n>th generation ancestor of the named
   commit object, following only the first parents.  I.e. '<rev>{tilde}3' is
@@ -159,12 +161,12 @@ thing no matter the case.
   '<rev>{caret}0'
   is a short-hand for '<rev>{caret}\{commit\}'.
 +
-'rev{caret}\{object\}' can be used to make sure 'rev' names an
-object that exists, without requiring 'rev' to be a tag, and
-without dereferencing 'rev'; because a tag is already an object,
+'<rev>{caret}\{object\}' can be used to make sure '<rev>' names an
+object that exists, without requiring '<rev>' to be a tag, and
+without dereferencing '<rev>'; because a tag is already an object,
 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
+'<rev>{caret}\{tag\}' can be used to ensure that '<rev>' identifies an
 existing tag object.
 
 '<rev>{caret}{}', e.g. 'v0.99.8{caret}{}'::
@@ -194,19 +196,16 @@ existing tag object.
   Depending on the given text, the shell's word splitting rules might
   require additional quoting.
 
-'<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
+'<rev>:<path>', e.g. 'HEAD:README', 'master:./README'::
   A suffix ':' followed by a path names the blob or tree
   at the given path in the tree-ish object named by the part
   before the colon.
-  ':path' (with an empty part before the colon)
-  is a special case of the syntax described next: content
-  recorded in the index at the given path.
   A path starting with './' or '../' is relative to the current working directory.
   The given path will be converted to be relative to the working tree's root directory.
   This is most useful to address a blob or tree from a commit or tree that has
   the same tree structure as the working tree.
 
-':<n>:<path>', e.g. ':0:README', ':README'::
+':[<n>:]<path>', e.g. ':0:README', ':README'::
   A colon, optionally followed by a stage number (0 to 3) and a
   colon, followed by a path, names a blob object in the
   index at the given path. A missing stage number (and the colon
@@ -302,7 +301,7 @@ The 'r1{caret}@' notation means all parents of 'r1'.
 The 'r1{caret}!' notation includes commit 'r1' but excludes all of its parents.
 By itself, this notation denotes the single commit 'r1'.
 
-The '<rev>{caret}-<n>' notation includes '<rev>' but excludes the <n>th
+The '<rev>{caret}-[<n>]' notation includes '<rev>' but excludes the <n>th
 parent (i.e. a shorthand for '<rev>{caret}<n>..<rev>'), with '<n>' = 1 if
 not given. This is typically useful for merge commits where you
 can just pass '<commit>{caret}-' to get all the commits in the branch