sieve: Add examples

docs/core/config/sieve/extensions/duplicate.md

@@ -41,3 +41,32 @@ sieve_script personal {
 sieve_duplicate_default_period = 1h
 sieve_duplicate_max_period = 1d
 ```
+
+## Sieve Example
+
+```sieve
+require ["duplicate"];
+
+if duplicate {
+  discard;
+  stop;
+}
+```
+
+This example discards duplicate messages based on the default message ID tracking.
+
+## Advanced Sieve Example
+
+```sieve
+require ["duplicate", "fileinto"];
+
+if duplicate :header "Message-ID" {
+  fileinto "Duplicates";
+  stop;
+}
+
+fileinto "Inbox";
+```
+
+This example uses the `Message-ID` header explicitly and files duplicate
+messages into a dedicated mailbox instead of discarding them.

docs/core/config/sieve/extensions/editheader.md

@@ -40,3 +40,15 @@ sieve_editheader_header X-Seen {
   forbid_delete = yes
 }
 ```
+
+## Sieve Example
+
+```sieve
+require ["editheader"];
+
+deleteheader "X-Spam-Flag";
+addheader "X-Processed-By" "Dovecot Sieve";
+```
+
+This example removes an existing header field and adds a new header field to
+mark the message as processed.

docs/core/config/sieve/extensions/include.md

@@ -24,3 +24,14 @@ The include extension is available by default.
 ### Settings
 
 <SettingsComponent tag="sieve-include" level="3" />
+
+## Sieve Example
+
+```sieve
+require ["include"];
+
+include :personal "spam_rules";
+```
+
+This example includes a personal Sieve script named `spam_rules` from the
+user's script storage.

docs/core/config/sieve/extensions/spamtest_virustest.md

@@ -125,3 +125,16 @@ sieve_virustest_text_value {
 }
 ```
 :::
+
+## Sieve Example
+
+```sieve
+require ["spamtest", "fileinto", "relational", "comparator-i;ascii-numeric"];
+
+if spamtest :value "ge" :comparator "i;ascii-numeric" "5" {
+  fileinto "Spam";
+}
+```
+
+This example files messages into the Spam folder when the spam score
+meets or exceeds the configured threshold.

docs/core/config/sieve/extensions/vacation.md

@@ -109,3 +109,15 @@ sieve_vacation_default_period = 10d
 # Thirty days at maximum
 sieve_vacation_max_period = 30d
 ```
+
+## Sieve Example
+
+```sieve
+require ["vacation"];
+
+vacation :days 7
+  :subject "Out of office"
+  "I am currently away and will reply when I return.";
+```
+
+This example sends an automatic reply at most once every 7 days per sender.

docs/core/config/sieve/extensions/variables.md

@@ -17,3 +17,20 @@ The variables extension is available by default.
 ### Settings
 
 <SettingsComponent tag="sieve-variables" level="3" />
+
+## Sieve Example
+
+```sieve
+require ["variables", "header", "fileinto"];
+
+if header :matches "Subject" "*" {
+  set "subject" "${1}";
+}
+
+if string :contains "${subject}" "report" {
+  fileinto "Reports";
+}
+```
+
+This example extracts the Subject header into a variable and files matching
+messages into a folder based on its contents.

docs/core/plugins/sieve_extprograms.md

@@ -269,3 +269,14 @@ the sender address and a time interval specified in seconds. The time
 interval is used to specify the minimum amount of time that needs to have
 passed since the sender was last seen. If the script returns exit code 0,
 then message is redirected in the Sieve script shown above.
+
+## Sieve Example
+
+```sieve
+require ["vnd.dovecot.pipe"];
+
+pipe "process-message";
+```
+
+This example pipes the message to an external program named
+`process-message`, which must be configured and available via the plugin.