Rename master branch to main

And remove all references to master (even unrelated ones). Everyone with
a local clone will need to update it;
[instructions](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-branches-in-your-repository/renaming-a-branch#updating-a-local-clone-after-a-branch-name-changes):

``` sh
git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a
```

Author: theory

Makefile

@@ -470,7 +470,7 @@ updatecheck_deps: pgtap-version-$(UPDATE_FROM) test/sql/update.sql
 # pg_regress --launcher not supported prior to 9.1
 # There are some other failures in 9.1 and 9.2 (see https://travis-ci.org/decibel/pgtap/builds/358206497).
 # TODO: find something that can generically compare majors (ie: GE91 from
-# https://github.com/decibel/pgxntool/blob/master/base.mk).
+# https://github.com/decibel/pgxntool/blob/0.1.10/base.mk).
 updatecheck_setup: updatecheck_deps
 	@if echo $(VERSION) | grep -qE "8[.]|9[.][012]"; then echo "updatecheck is not supported prior to 9.3"; exit 1; fi
 	$(eval SETUP_SCH = test/schedule/update.sch)

contrib/pgtap.spec

@@ -5,7 +5,7 @@ Release:	  1%{?dist}
 Group:		  Applications/Databases
 License:	  PostgreSQL
 URL:		    https://pgtap.org/
-Source0:	  https://master.pgxn.org/dist/pgtap/%{version}/pgtap-%{version}.zip
+Source0:    https://api.pgxn.org/dist/pgtap/%{version}/pgtap-%{version}.zip
 BuildRoot:	%{_tmppath}/%{name}-%{version}-%{release}-root
 Provides:   %{name}
 Provides:   %{name}-core

release.md

@@ -75,7 +75,7 @@ Here are the steps to take to make a release of pgTAP:
 
     +   Commit the changes, but don't push them yet.
 
-*   Go back to the `master` branch and proofread the additions to the `Changes`
+*   Go back to the `main` branch and proofread the additions to the `Changes`
     file since the last release. Make sure all relevant changes are recorded
     there, and that any typos or formatting errors are corrected.
 

tools/util.sh

@@ -1,4 +1,4 @@
-# Adapted from https://github.com/decibel/db_tools/blob/master/lib/util.sh
+# Adapted from https://github.com/decibel/db_tools/blob/0.1.10/lib/util.sh
 
 ME=`basename $0`