show --continue/skip etc. consistently in synopsis

The synopsis for am shows the command mode options as
    (--continue | --skip | --abort | --quit)
They are on a single line and in parenthesis as they are not
optional. Fix the merge and rebase docs to match this style.

Signed-off-by: Phillip Wood <[email protected]>
---
This patch is based on top of nd/merge-quit.
The docs for cherry-pick/revert are updated to this style by
https://public-inbox.org/git/[email protected]/T/#u

Author: phillipwood

Documentation/git-merge.txt

@@ -13,8 +13,7 @@ SYNOPSIS
 	[-s <strategy>] [-X <strategy-option>] [-S[<keyid>]]
 	[--[no-]allow-unrelated-histories]
 	[--[no-]rerere-autoupdate] [-m <msg>] [-F <file>] [<commit>...]
-'git merge' --abort
-'git merge' --continue
+'git merge' (--continue | --skip | --abort | --quit)
 
 DESCRIPTION
 -----------

Documentation/git-rebase.txt

@@ -12,7 +12,7 @@ SYNOPSIS
 	[<upstream> [<branch>]]
 'git rebase' [-i | --interactive] [<options>] [--exec <cmd>] [--onto <newbase>]
 	--root [<branch>]
-'git rebase' --continue | --skip | --abort | --quit | --edit-todo | --show-current-patch
+'git rebase' (--continue | --skip | --abort | --quit | --edit-todo | --show-current-patch)
 
 DESCRIPTION
 -----------