parse-options: multi-word argh should use dash to separate words

"When you need to use space, use dash" is a strange way to say that
you must not use a space.  Because it is more common for the command
line descriptions to use dashed-multi-words, you do not even want to
use spaces in these places.  Rephrase the documentation to avoid
this strangeness.

Fix a few existing multi-word argument help strings, i.e.

 - GPG key-ids given to -S/--gpg-sign are "key-id";
 - Refs used for storing notes are "notes-ref"; and
 - Expiry timestamps given to --expire are "expiry-date".

and update the corresponding documentation pages.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-cherry-pick.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git cherry-pick' [--edit] [-n] [-m parent-number] [-s] [-x] [--ff]
-		  [-S[<keyid>]] <commit>...
+		  [-S[<key-id>]] <commit>...
 'git cherry-pick' --continue
 'git cherry-pick' --quit
 'git cherry-pick' --abort
@@ -101,8 +101,8 @@ effect to your index in a row.
 --signoff::
 	Add Signed-off-by line at the end of the commit message.
 
--S[<keyid>]::
---gpg-sign[=<keyid>]::
+-S[<key-id>]::
+--gpg-sign[=<key-id>]::
 	GPG-sign commits.
 
 --ff::

Documentation/git-commit.txt

@@ -13,7 +13,7 @@ SYNOPSIS
 	   [-F <file> | -m <msg>] [--reset-author] [--allow-empty]
 	   [--allow-empty-message] [--no-verify] [-e] [--author=<author>]
 	   [--date=<date>] [--cleanup=<mode>] [--[no-]status]
-	   [-i | -o] [-S[<keyid>]] [--] [<file>...]
+	   [-i | -o] [-S[<key-id>]] [--] [<file>...]
 
 DESCRIPTION
 -----------

Documentation/git-merge.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git merge' [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
-	[-s <strategy>] [-X <strategy-option>] [-S[<keyid>]]
+	[-s <strategy>] [-X <strategy-option>] [-S[<key-id>]]
 	[--[no-]rerere-autoupdate] [-m <msg>] [<commit>...]
 'git merge' <msg> HEAD <commit>...
 'git merge' --abort

Documentation/git-notes.txt

@@ -14,7 +14,7 @@ SYNOPSIS
 'git notes' append [-F <file> | -m <msg> | (-c | -C) <object>] [<object>]
 'git notes' edit [<object>]
 'git notes' show [<object>]
-'git notes' merge [-v | -q] [-s <strategy> ] <notes_ref>
+'git notes' merge [-v | -q] [-s <strategy> ] <notes-ref>
 'git notes' merge --commit [-v | -q]
 'git notes' merge --abort [-v | -q]
 'git notes' remove [--ignore-missing] [--stdin] [<object>...]

Documentation/git-rev-parse.txt

@@ -290,14 +290,14 @@ The lines after the separator describe the options.
 Each line of options has this format:
 
 ------------
-<opt_spec><flags>*<arg_hint>? SP+ help LF
+<opt-spec><flags>*<arg-hint>? SP+ help LF
 ------------
 
-`<opt_spec>`::
+`<opt-spec>`::
 	its format is the short option character, then the long option name
 	separated by a comma. Both parts are not required, though at least one
 	is necessary. `h,help`, `dry-run` and `f` are all three correct
-	`<opt_spec>`.
+	`<opt-spec>`.
 
 `<flags>`::
 	`<flags>` are of `*`, `=`, `?` or `!`.
@@ -313,11 +313,11 @@ Each line of options has this format:
 
 	* Use `!` to not make the corresponding negated long option available.
 
-`<arg_hint>`::
-	`<arg_hint>`, if specified, is used as a name of the argument in the
-	help output, for options that take arguments. `<arg_hint>` is
-	terminated by the first whitespace. When you need to use space in the
-	argument hint use dash instead.
+`<arg-hint>`::
+	`<arg-hint>`, if specified, is used as a name of the argument in the
+	help output, for options that take arguments. `<arg-hint>` is
+	terminated by the first whitespace.  It is customary to use a
+	dash to separate words in a multi-word argument hint.
 
 The remainder of the line, after stripping the spaces, is used
 as the help associated to the option.

Documentation/git-revert.txt

@@ -8,7 +8,7 @@ git-revert - Revert some existing commits
 SYNOPSIS
 --------
 [verse]
-'git revert' [--[no-]edit] [-n] [-m parent-number] [-s] [-S[<keyid>]] <commit>...
+'git revert' [--[no-]edit] [-n] [-m parent-number] [-s] [-S[<key-id>]] <commit>...
 'git revert' --continue
 'git revert' --quit
 'git revert' --abort
@@ -80,8 +80,8 @@ more details.
 This is useful when reverting more than one commits'
 effect to your index in a row.
 
--S[<keyid>]::
---gpg-sign[=<keyid>]::
+-S[<key-id>]::
+--gpg-sign[=<key-id>]::
 	GPG-sign commits.
 
 -s::