help: apply bulk fixes for indentation and literal blocking issues

There are some paragraphs, which aren't rendered in online help as
expected because of indentation and literal blocking issues.

- hgext/rebase.py

  - paragraph before example code ends with ":", which treats
    subsequent indented paragraphs as normal block

    => replace ":" with "::" to treat subsequent paragraphs as literal block

- help/pager.txt

  - paragraph before a list of --pager option values ends with "::",
    which treats subsequent indented paragraphs as literal block

    => replace "::" with ":" to treat subsequent paragraphs as normal block

  - the second line of explanation for no/off --pager option value is
    indented incorrectly (this also causes failure of "make" in doc)

    => indent correctly

- help/revisions.txt

  - explanation following example code of "[revsetalias]" section
    isn't suitable for literal block

    => un-indent explanation paragraph to treat it as normal block

  - indentation of "For example" before example of tag() revset
    predicate matching is meaningless

  - descriptive text for tag() revset predicate matching isn't
    suitable for literal block

    => un-indent concatenated two paragraphs to treat them as normal block

hgext/rebase.py

@@ -665,7 +665,7 b' def rebase(ui, repo, **opts):'
     Configuration Options:
 
     You can make rebase require a destination if you set the following config
-    option:
+    option::
 
       [commands]
       rebase.requiredest = True

mercurial/help/pager.txt

@@ -20,12 +20,12 b' To ignore global commands like :hg:`vers'
 to specify them in your user configuration file.
 
 To control whether the pager is used at all for an individual command,
-you can use --pager=<value>::
+you can use --pager=<value>:
 
   - use as needed: `auto`.
   - require the pager: `yes` or `on`.
   - suppress the pager: `no` or `off` (any unrecognized value
-  will also work).
+    will also work).
 
 To globally turn off all attempts to use a pager, set::
 

mercurial/help/revisions.txt

@@ -109,10 +109,10 b' These are the supported infix operators:'
     [revsetalias]
     issue(a1) = grep(r'\bissue[ :]?' ## a1 ## r'\b|\bbug\(' ## a1 ## r'\)')
 
-    ``issue(1234)`` is equivalent to
-    ``grep(r'\bissue[ :]?1234\b|\bbug\(1234\)')``
-    in this case. This matches against all of "issue 1234", "issue:1234",
-    "issue1234" and "bug(1234)".
+  ``issue(1234)`` is equivalent to
+  ``grep(r'\bissue[ :]?1234\b|\bbug\(1234\)')``
+  in this case. This matches against all of "issue 1234", "issue:1234",
+  "issue1234" and "bug(1234)".
 
 There is a single postfix operator:
 
@@ -132,9 +132,8 b' Matching is case-sensitive, unless other'
 insensitive match on a case-sensitive predicate, use a regular expression,
 prefixed with ``(?i)``.
 
-  For example::
-
-    ``tag(r're:(?i)release')`` matches "release" or "RELEASE" or "Release", etc
+For example, ``tag(r're:(?i)release')`` matches "release" or "RELEASE"
+or "Release", etc
 
 Predicates
 ==========