Documentation cvs: Clarify when a bare repository is needed

New users sometimes import a project and then immediately
try to use the imported repository as a central shared repository.
This provides pointers about setting up a bare repository for that
in the parts of the documentation dealing with CVS migration.

Signed-off-by: Matthew Ogilvie <mmogilvi_git@miniinfo.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-cvsimport.txt

@@ -31,6 +31,12 @@ to work with; after that, you need to 'git merge' incremental imports, or
 any CVS branches, yourself.  It is advisable to specify a named remote via
 -r to separate and protect the incoming branches.
 
+If you intend to set up a shared public repository that all developers can
+read/write, or if you want to use linkgit:git-cvsserver[1], then you
+probably want to make a bare clone of the imported repository,
+and use the clone as the shared repository.
+See linkgit:gitcvs-migration[7].
+
 
 OPTIONS
 -------

Documentation/git-cvsserver.txt

@@ -133,6 +133,9 @@ write access to the log file and to the database (see
 <<dbbackend,Database Backend>>. If you want to offer write access over
 SSH, the users of course also need write access to the git repository itself.
 
+You also need to ensure that each repository is "bare" (without a git index
+file) for `cvs commit` to work. See linkgit:gitcvs-migration[7].
+
 [[configaccessmethod]]
 All configuration variables can also be overridden for a specific method of
 access. Valid method names are "ext" (for SSH access) and "pserver". The

Documentation/gitcvs-migration.txt

@@ -143,6 +143,11 @@ work, you must not modify the imported branches; instead, create new
 branches for your own changes, and merge in the imported branches as
 necessary.
 
+If you want a shared repository, you will need to make a bare clone
+of the imported directory, as described above. Then treat the imported
+directory as another development clone for purposes of merging
+incremental imports.
+
 Advanced Shared Repository Management
 -------------------------------------