lib: add NOTMUCH_STATUS_DATABASE_EXISTS

It is desirable to distinguish between attempting to create a database
that already exists, and more fatal errors like permission problems.

bindings/python-cffi/notmuch2/_build.py

@@ -51,6 +51,7 @@ ffibuilder.cdef(
         NOTMUCH_STATUS_FAILED_CRYPTO_CONTEXT_CREATION,
         NOTMUCH_STATUS_UNKNOWN_CRYPTO_PROTOCOL,
         NOTMUCH_STATUS_NO_CONFIG,
+        NOTMUCH_STATUS_DATABASE_EXISTS,
         NOTMUCH_STATUS_LAST_STATUS
     } notmuch_status_t;
     typedef enum {

bindings/python-cffi/notmuch2/_errors.py

@@ -52,6 +52,8 @@ class NotmuchError(Exception):
                 IllegalArgumentError,
             capi.lib.NOTMUCH_STATUS_NO_CONFIG:
                 NoConfigError,
+            capi.lib.NOTMUCH_STATUS_DATABASE_EXISTS:
+                DatabaseExistsError,
         }
         return types[status]
 
@@ -97,6 +99,7 @@ class UpgradeRequiredError(NotmuchError): pass
 class PathError(NotmuchError): pass
 class IllegalArgumentError(NotmuchError): pass
 class NoConfigError(NotmuchError): pass
+class DatabaseExistsError(NotmuchError): pass
 
 class ObjectDestroyedError(NotmuchError):
     """The object has already been destroyed and it's memory freed.

lib/notmuch.h

@@ -212,6 +212,10 @@ typedef enum _notmuch_status {
      * Unable to load a config file
      */
     NOTMUCH_STATUS_NO_CONFIG,
+    /**
+     * Database exists, so not (re)-created
+     */
+    NOTMUCH_STATUS_DATABASE_EXISTS,
     /**
      * Not an actual status value. Just a way to find out how many
      * valid status values there are.