DOC: Rename master to main

src/doc/crawler.rst

@@ -3,7 +3,7 @@ CaosDB Crawler
 ==============
 
 The `CaosDB
-crawler <https://gitlab.com/caosdb/caosdb-advanced-user-tools/blob/master/src/caosadvancedtools/crawler.py>`__
+crawler <https://gitlab.com/caosdb/caosdb-advanced-user-tools/blob/main/src/caosadvancedtools/crawler.py>`__
 is a tool for the automated insertion or update of entities in CaosDB.
 Typically, a file structure is crawled, but other things can be crawled as well.
 For example tables or HDF5 files.
@@ -75,7 +75,7 @@ The crawler can be executed directly via a python script (usually called
 ``crawl.py``). The script prints the progress and reports potential
 problems. The exact behavior depends on your setup. However, you can
 have a look at the example in the
-`tests <https://gitlab.com/caosdb/caosdb-advanced-user-tools/-/blob/master/integrationtests/full_test/crawl.py>`__.
+`tests <https://gitlab.com/caosdb/caosdb-advanced-user-tools/-/blob/main/integrationtests/full_test/crawl.py>`__.
 
 .. Note:: The crawler depends on the CaosDB Python client, so make sure to install :doc:`pycaosdb
           <caosdb-pylib:getting_started>`.