convert: show example splice, author, and branch map entries in help

Also document that

- empty lines are skipped and comment are supported in author map

- whitespace is not allowed in branch map entries since we split on it
  when parsing the file

hgext/convert/__init__.py

@@ -73,8 +73,11 def convert(ui, src, dest=None, revmapfi
     The [username mapping] file is a simple text file that maps each
     source commit author to a destination commit author. It is handy
     for source SCMs that use unix logins to identify authors (eg:
-    CVS). One line per author mapping and the line format is:
-    srcauthor=whatever string you want
+    CVS). One line per author mapping and the line format is::
+
+      source author = destination author
+
+    Empty lines and lines starting with a ``#`` are ignored.
 
     The filemap is a file that allows filtering and remapping of files
     and directories. Each line can contain one of the following
@@ -104,7 +107,11 def convert(ui, src, dest=None, revmapfi
     useful if you want to e.g. give a Subversion merge two parents, or
     graft two disconnected series of history together. Each entry
     contains a key, followed by a space, followed by one or two
-    comma-separated values. The key is the revision ID in the source
+    comma-separated values::
+
+      key parent1, parent2
+
+    The key is the revision ID in the source
     revision control system whose parents should be modified (same
     format as a key in .hg/shamap). The values are the revision IDs
     (in either the source or destination revision control system) that
@@ -118,11 +125,15 def convert(ui, src, dest=None, revmapfi
     conjunction with a splicemap, it allows for a powerful combination
     to help fix even the most badly mismanaged repositories and turn them
     into nicely structured Mercurial repositories. The branchmap contains
-    lines of the form "original_branch_name new_branch_name".
-    "original_branch_name" is the name of the branch in the source
-    repository, and "new_branch_name" is the name of the branch is the
-    destination repository. This can be used to (for instance) move code
-    in one repository from "default" to a named branch.
+    lines of the form::
+
+      original_branch_name new_branch_name
+
+    where "original_branch_name" is the name of the branch in the
+    source repository, and "new_branch_name" is the name of the branch
+    is the destination repository. No whitespace is allowed in the
+    branch names. This can be used to (for instance) move code in one
+    repository from "default" to a named branch.
 
     Mercurial Source
     ----------------

tests/test-convert.out

@@ -54,7 +54,11 convert a foreign SCM repository to a Me
     The [username mapping] file is a simple text file that maps each source
     commit author to a destination commit author. It is handy for source SCMs
     that use unix logins to identify authors (eg: CVS). One line per author
-    mapping and the line format is: srcauthor=whatever string you want
+    mapping and the line format is:
+
+      source author = destination author
+
+    Empty lines and lines starting with a "#" are ignored.
 
     The filemap is a file that allows filtering and remapping of files and
     directories. Each line can contain one of the following directives:
@@ -81,24 +85,32 convert a foreign SCM repository to a Me
     letting you specify the parents of a revision. This is useful if you want
     to e.g. give a Subversion merge two parents, or graft two disconnected
     series of history together. Each entry contains a key, followed by a
-    space, followed by one or two comma-separated values. The key is the
-    revision ID in the source revision control system whose parents should be
-    modified (same format as a key in .hg/shamap). The values are the revision
-    IDs (in either the source or destination revision control system) that
-    should be used as the new parents for that node. For example, if you have
-    merged "release-1.0" into "trunk", then you should specify the revision on
-    "trunk" as the first parent and the one on the "release-1.0" branch as the
-    second.
+    space, followed by one or two comma-separated values:
+
+      key parent1, parent2
+
+    The key is the revision ID in the source revision control system whose
+    parents should be modified (same format as a key in .hg/shamap). The
+    values are the revision IDs (in either the source or destination revision
+    control system) that should be used as the new parents for that node. For
+    example, if you have merged "release-1.0" into "trunk", then you should
+    specify the revision on "trunk" as the first parent and the one on the
+    "release-1.0" branch as the second.
 
     The branchmap is a file that allows you to rename a branch when it is
     being brought in from whatever external repository. When used in
     conjunction with a splicemap, it allows for a powerful combination to help
     fix even the most badly mismanaged repositories and turn them into nicely
     structured Mercurial repositories. The branchmap contains lines of the
-    form "original_branch_name new_branch_name". "original_branch_name" is the
-    name of the branch in the source repository, and "new_branch_name" is the
-    name of the branch is the destination repository. This can be used to (for
-    instance) move code in one repository from "default" to a named branch.
+    form:
+
+      original_branch_name new_branch_name
+
+    where "original_branch_name" is the name of the branch in the source
+    repository, and "new_branch_name" is the name of the branch is the
+    destination repository. No whitespace is allowed in the branch names. This
+    can be used to (for instance) move code in one repository from "default"
+    to a named branch.
 
     Mercurial Source
     ----------------