[CI:DOCS] fix default branch links

* Replace https://github.com/containers/podman/blob/master
  with https://github.com/containers/podman/blob/main
  to match the new default branch "main". Previously
  the default branch was "master". The substitutions were
  made in the documentation but not the code.

Signed-off-by: Erik Sjölund <erik.sjolund@gmail.com>

docs/tutorials/mac_client.md

@@ -1,2 +1,2 @@
-# [Podman Mac Client tutorial](https://github.com/containers/podman/blob/master/docs/tutorials/mac_win_client.md)
-This tutorial has moved! You can find out how to set up Podman on macOS (as well as Windows) [here](https://github.com/containers/podman/blob/master/docs/tutorials/mac_win_client.md)
+# [Podman Mac Client tutorial](https://github.com/containers/podman/blob/main/docs/tutorials/mac_win_client.md)
+This tutorial has moved! You can find out how to set up Podman on macOS (as well as Windows) [here](https://github.com/containers/podman/blob/main/docs/tutorials/mac_win_client.md)

docs/tutorials/podman_tutorial.md

@@ -5,7 +5,7 @@ Podman is a utility provided as part of the libpod library.  It can be used to c
 containers. The following tutorial will teach you how to set up Podman and perform some basic
 commands with Podman.
 
-If you are running on a Mac or Windows PC, you should instead follow the [Mac and Windows tutorial](https://github.com/containers/podman/blob/master/docs/tutorials/mac_win_client.md)
+If you are running on a Mac or Windows PC, you should instead follow the [Mac and Windows tutorial](https://github.com/containers/podman/blob/main/docs/tutorials/mac_win_client.md)
 to set up the remote Podman client.
 
 **NOTE**: the code samples are intended to be run as a non-root user, and use `sudo` where
@@ -13,7 +13,7 @@ root escalation is required.
 
 ## Installing Podman
 
-For installing or building Podman, please see the [installation instructions](https://github.com/containers/podman/blob/master/install.md).
+For installing or building Podman, please see the [installation instructions](https://github.com/containers/podman/blob/main/install.md).
 
 ## Familiarizing yourself with Podman
 

docs/tutorials/podman_tutorial_cn.md

@@ -7,14 +7,14 @@ Podman是由libpod库提供一个实用的程序，可以被用于创建和管
 下面的教程会教你如何启动 Podman 并使用 Podman 执行一些基本的命令。
 
 如果你正在使用 Mac 或者 Windows
-，你应该先查看[Mac 和 Windows 使用说明](https://github.com/containers/podman/blob/master/docs/tutorials/mac_win_client.md)来设置 Podman
+，你应该先查看[Mac 和 Windows 使用说明](https://github.com/containers/podman/blob/main/docs/tutorials/mac_win_client.md)来设置 Podman
 远程客户端。
 
 **注意**：示例中所有命令皆以非 root 的用户运行，必要的时候通过 `sudo` 命令来获取 root 权限。
 
 ## 安装Podman
 
-安装或者编译 Podman ，请参照[安装说明](https://github.com/containers/podman/blob/master/install.md)。
+安装或者编译 Podman ，请参照[安装说明](https://github.com/containers/podman/blob/main/install.md)。
 
 ## 熟悉podman
 

docs/tutorials/remote_client.md

@@ -5,7 +5,7 @@ The purpose of the Podman remote-client is to allow users to interact with a Pod
 
 The remote client takes advantage of a client-server model. You need Podman installed on a Linux machine or VM that also has the SSH daemon running. On the local operating system, when you execute a Podman command, Podman connects to the server via SSH. It then connects to the Podman service by using systemd socket activation, and hitting our [Rest API](https://docs.podman.io/en/latest/_static/api.html). The Podman commands are executed on the server. From the client's point of view, it seems like Podman runs locally.
 
-This tutorial is for running Podman remotely on Linux. If you are using a Mac or a Windows PC, please follow the [Mac and Windows tutorial](https://github.com/containers/podman/blob/master/docs/tutorials/mac_win_client.md)
+This tutorial is for running Podman remotely on Linux. If you are using a Mac or a Windows PC, please follow the [Mac and Windows tutorial](https://github.com/containers/podman/blob/main/docs/tutorials/mac_win_client.md)
 
 ## Obtaining and installing Podman
 
@@ -113,4 +113,4 @@ You can use the Podman remote clients to manage your containers running on a Lin
 See the [Troubleshooting](../../troubleshooting.md) document if you run into issues.
 
 ## History
-Adapted from the [Mac and Windows tutorial](https://github.com/containers/podman/blob/master/docs/tutorials/mac_win_client.md)
+Adapted from the [Mac and Windows tutorial](https://github.com/containers/podman/blob/main/docs/tutorials/mac_win_client.md)