doc/backup: link to exit code for scripting section

doc/040_backup.rst

@@ -778,11 +778,12 @@ environment variables and configuration files; see their respective manuals.
 Exit status codes
 *****************
 
-Restic returns one of the following exit status codes after the backup command is run:
+Restic returns an exit status code after the backup command is run:
 
 * 0 when the backup was successful (snapshot with all source files created)
 * 1 when there was a fatal error (no snapshot created)
 * 3 when some source files could not be read (incomplete snapshot with remaining files created)
+* further exit codes are documented in :ref:`exit-codes`.
 
 Fatal errors occur for example when restic is unable to write to the backup destination, when
 there are network connectivity issues preventing successful communication, or when an invalid
@@ -795,5 +796,5 @@ file read errors that occurred while running the backup. If there are errors of
 restic will still try to complete the backup run with all the other files, and create a
 snapshot that then contains all but the unreadable files.
 
-One can use these exit status codes in scripts and other automation tools, to make them aware of
-the outcome of the backup run. To manually inspect the exit code in e.g. Linux, run ``echo $?``.
+For use of these exit status codes in scripts and other automation tools, see :ref:`exit-codes`.
+To manually inspect the exit code in e.g. Linux, run ``echo $?``.

doc/075_scripting.rst

@@ -39,6 +39,8 @@ Note that restic will also return exit code ``1`` if a different error is encoun
 If there are no errors, restic will return a zero exit code and print the repository
 metadata.
 
+.. _exit-codes:
+
 Exit codes
 **********