Document the hooks feature

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

contrib/caldav/README

@@ -26,10 +26,25 @@ argument. You can choose between the following initialization modes:
     --init=keep-remote Remove all local calcurse items and import remote objects
     --init=keep-local  Remove all remote objects and push local calcurse items
     --init=two-way     Copy local objects to the CalDAV server and vice versa
- 
+
 For subsequent calcurse-caldav invocations, you don't need to specify any
 additional parameters.
 
+Hooks
+-----
+
+You can place scripts in `$HOME/.calcurse/caldav/hooks/` to trigger actions at
+certain events. To enable a hook, add a script with one of the following names
+to this directory. Also make sure the scripts are executable.
+
+*pre-sync*::
+  Executed before the data files are synchronized.
+*post-sync*::
+  Executed after the data files are synchronized.
+
+Some examples can be found in the `contrib/caldav/hooks/` directory of the
+calcurse source tree.
+
 How It Works
 ------------
 

doc/calcurse.1.txt

@@ -413,6 +413,25 @@ internal representation and were designed to be used for scripting:
 * *(hash)*
 * *(raw)*
 
+Hooks
+-----
+
+You can place scripts in `$HOME/.calcurse/hooks/` to trigger actions at certain
+events. To enable a hook, add a script with one of the following names to this
+directory. Also make sure the scripts are executable.
+
+*pre-load*::
+  Executed before the data files are loaded.
+*post-load*::
+  Executed after the data files are saved.
+*pre-save*::
+  Executed before the data files are loaded.
+*post-save*::
+  Executed after the data files are saved.
+
+Some examples can be found in the `contrib/hooks/` directory of the calcurse
+source tree.
+
 Notes
 -----
 

doc/manual.txt

@@ -632,6 +632,25 @@ The following environment variables affect the way `calcurse` operates:
   Specifies the default viewer to be used for reading notes.  If this variable
   is not set, then `/usr/bin/less` is used.
 
+Hooks
+~~~~~
+
+You can place scripts in `$HOME/.calcurse/hooks/` to trigger actions at certain
+events. To enable a hook, add a script with one of the following names to this
+directory. Also make sure the scripts are executable.
+
+*pre-load*::
+  Executed before the data files are loaded.
+*post-load*::
+  Executed after the data files are saved.
+*pre-save*::
+  Executed before the data files are loaded.
+*post-save*::
+  Executed after the data files are saved.
+
+Some examples can be found in the `contrib/hooks/` directory of the calcurse
+source tree.
+
 User interface
 ~~~~~~~~~~~~~~