X-Git-Url: https://git.cworth.org/git?a=blobdiff_plain;f=doc%2Fman1%2Fnotmuch.rst;fp=doc%2Fman1%2Fnotmuch.rst;h=c488f12a9e7a58193486b5dd5fdf76fe31f62057;hb=0558c46f78e3abc4d9ee27cd135b29ddf356073d;hp=c6ee30366264016846701ee4b3c4a9d4df343877;hpb=ceeeebec2fdc97f8d323a3a7080da1be9e8e7f24;p=notmuch

diff --git a/doc/man1/notmuch.rst b/doc/man1/notmuch.rst
index c6ee3036..c488f12a 100644
--- a/doc/man1/notmuch.rst
+++ b/doc/man1/notmuch.rst
@@ -130,14 +130,16 @@ and to restore from that dump.
 The :any:`notmuch-config(1)` command can be used to get or set
 settings in the notmuch configuration file.
 
-CUSTOM COMMANDS
----------------
+EXTERNAL COMMANDS
+-----------------
 
 If the given command is not known to notmuch, notmuch tries to execute
 the external **notmuch-<subcommand>** in :envvar:`PATH` instead. This
 allows users to have their own notmuch related tools to be run via the
 notmuch command. By design, this does not allow notmuch's own commands
-to be overridden using external commands.
+to be overridden using external commands.  The environment variable
+:envvar:`NOTMUCH_CONFIG` will be set according to :option:`--config`,
+if the latter is present.
 
 OPTION SYNTAX
 -------------
@@ -153,6 +155,23 @@ equivalent:
    notmuch --config:alt-config config get user.name
    notmuch --config alt-config config get user.name
 
+.. _duplicate-files:
+
+DUPLICATE MESSAGE FILES
+=======================
+
+Notmuch considers the :mailheader:`Message-ID` to be the primary
+identifier of message. Per :rfc:`5322` the :mailheader:`Message-ID` is
+supposed to be globally unique, but this fails in two distinct
+ways. When you receive copies of a message via a mechanism like
+:mailheader:`Cc` or via a mailing list, the copies are typically
+interchangeable. In the case of some broken mail sending software, the
+same :mailheader:`Message-ID` is used for completely unrelated
+messages. The options :option:`search --duplicate` and :option:`show
+--duplicate` options provide the user with control over which message
+file is displayed. Front ends will need to provide their own
+interface, see e.g. the Emacs front-end :any:`emacs-show-duplicates`.
+
 ENVIRONMENT
 ===========