Clarify documentation of git-cvsserver, particularly in relation to git-shell

For SSH clients restricted to git-shell, CVS_SERVER does not have to be
specified, because git-shell understands the default value of 'cvs' to
mean git-cvsserver'. This makes it totally transparent to CVS users, but
the instruction to set up CVS access for people with real shell access
does not apply.

Previous wording mentioning GIT_AUTHOR, GIT_COMMITTER variables was
unclear that we really meant GIT_AUTHOR_(NAME|EMAIL), etc.

Note that the .ssh/environment file is a good place to set these, and that
the .bashrc is shell-specific. Add a bit of text to differentiate cvs -d
(setting CVSROOT) from cvs co -d (setting the name of the newly checked
out directory).  Removed an extra 'Example:' string.

Signed-off-by: Scott Collins <scc@ScottCollins.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-cvsserver.txt

@@ -110,7 +110,9 @@ cvs -d ":ext;CVS_SERVER=git-cvsserver:user@server/path/repo.git" co <HEAD_name>
 ------
 This has the advantage that it will be saved in your 'CVS/Root' files and
 you don't need to worry about always setting the correct environment
-variable.
+variable.  SSH users restricted to git-shell don't need to override the default
+with CVS_SERVER (and shouldn't) as git-shell understands `cvs` to mean
+git-cvsserver and pretends that the other end runs the real cvs better.
 --
 2. For each repo that you want accessible from CVS you need to edit config in
    the repo and add the following section.
@@ -141,25 +143,29 @@ allowing access over SSH.
         enabled=1
 ------
 --
-3. On the client machine you need to set the following variables.
-   CVSROOT should be set as per normal, but the directory should point at the
-   appropriate git repo. For example:
+3. If you didn't specify the CVSROOT/CVS_SERVER directly in the checkout command,
+   automatically saving it in your 'CVS/Root' files, then you need to set them
+   explicitly in your environment.  CVSROOT should be set as per normal, but the
+   directory should point at the appropriate git repo.  As above, for SSH clients
+   _not_ restricted to git-shell, CVS_SERVER should be set to git-cvsserver.
 +
 --
-For SSH access, CVS_SERVER should be set to git-cvsserver
-
-Example:
-
 ------
      export CVSROOT=:ext:user@server:/var/git/project.git
      export CVS_SERVER=git-cvsserver
 ------
 --
-4. For SSH clients that will make commits, make sure their .bashrc file
-   sets the GIT_AUTHOR and GIT_COMMITTER variables.
+4. For SSH clients that will make commits, make sure their server-side
+   .ssh/environment files (or .bashrc, etc., according to their specific shell)
+   export appropriate values for GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL,
+   GIT_COMMITTER_NAME, and GIT_COMMITTER_EMAIL.  For SSH clients whose login
+   shell is bash, .bashrc may be a reasonable alternative.
 
 5. Clients should now be able to check out the project. Use the CVS 'module'
-   name to indicate what GIT 'head' you want to check out. Example:
+   name to indicate what GIT 'head' you want to check out.  This also sets the
+   name of your newly checked-out directory, unless you tell it otherwise with
+   `-d <dir_name>`.  For example, this checks out 'master' branch to the
+   `project-master` directory:
 +
 ------
      cvs co -d project-master master